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Description
During the cold war but especially in the 1960's and 70's the USN desperately seeking ways to increase and extend it's amphibious assault forces. In that era born the first Amphibious Assault Ships and first helicopter carriers (the conversions of a number of Essex class fleet carriers) and later the true purpose built ship class the Iwo Jimas. These warships were excellent in bringing the troops and their equipment to the beaches and shorelines via helicopters but had two major disadvantages: providing fire support and providing landing ships to carry more heavier and powerful equipment to the battlezone like trucks, half tracks and especially tanks! The United States Marine Corps was always demanded of retaining larger calibre gun armed warships for the fleet to at least provide fire support for the troops in fighting, hence the United States Navy drawn up conversion plans of LPH (Landing Platform Helicopter) type designs for the North Carolina and Iowa classes.
The North Carolina conversion proposal of the early 1960's would had been quite expensive but on the other hand very significant redesign:
The redesigned ships would have carried at least 28 helicopters and 1.880 troops as well as 530tons of troop cargo and 200.000 gallons of gasoline. The armament would had been reduced to 8x2 3"/50 AA guns and the forward most 16" triple turret for trim, that is to balance the added weight around the ship. The cost of such a conversion at that time was estimated almost 31 million dollars!

The conversion of the Iowa class battleships was proposed in late 1961, early 1962 and would had entailed the following modifications:
Troops and helicopter deck would had replaced the aft triple 16"/50 gun turret, all light and all but the forwardmost 5"/38 guns to be removed and one the remaining 16" gun turrets to be modified to fire the Mark 23 or W23 15-20 kiloton yield nuclear shell.
Troop capacity was estimated to be 1.800 men with a landing craft carrying capacity of either 18x LCM-6 or 6x LCM-6 and 6x LCM-8
The Landing crafts would had been handled by two 35ton cranes on each side and they would had been stowed in cradles or davits.
Helicopter capacity was stated to be 30x CH-46 Sea Knights of which 20 could be carried in the Hanger and 10 on the flight deck.
For self defence a single ASROC was to be installed on the nose with an associates SQS-23 sonar for target acquisition.
The feasibility study was created by June showing a raised flight deck aft with crew accommodations directly below it and hanger with a single elevator below that, fuel storage would had been 100tons of aviation gasoline and 675 tons of JP-5 jet fuel. Full storage would amount 650m^2 or 7.000ft^2 of vehicles weighting around 250 tons and 2.800m^3 or 100.000ft^3 of cargo and equipment roughly weighting 1.600tons. For example as a comparison the Iwo Jimas could only carry 1.500 troops and 30x helicopters but no landing craft and thus could not operate in bad weather, even the converted Essex class carriers could only accommodate 1.650 marines and 40 helicopters!
The conversion of the Iowas was quite tempting because the associated cost of such a conversion per ship was stated 65 million dollars while an Essex conversion was 61 million and a new Iwo Jima was 47 million dollars. Not to mention that these ships was fast with a sustained speed of 29,6knots or 55km/h, able to provide heavy gun fire support and carry the same number of helicopters as the LPD, the combined bulk cargo of the CVH and LPD or 64% of the combined troop capacity.
However at this time the USN was facing money issues with much of the allocated founds by the congress went into the large fleet ballistic missile program, ASW modernisation of the fleet and new amphibious construction programs all competing for the same limited founds! Hence this attractive conversion proposal was cancelled soon after.

This drawing too was commissioned by yamato74

The designs had these characteristics:

Dimensions: 262,1m(wl), 270,4m (oa) x 33 x 11m
Displacement: unknown
Engines: 212.000shp General Electric / Westinghouse Steam Turbines, 4 shafts

Speed: 61km/h (33knots)
Range: 27.800km at 28km/h (15000nm at 15knots)
Armour: 178mm, Deck over machinery and magazines, 307mm Belt over machinery and magazines.
Armaments:
2x3 16"/50 (406mm/50) Mark 7 Cannons,
2x2 5"/38 (127mm/38) Mark 12 DP-AA Guns,

1x8 RUR-5 ASROCK ASWM,
20+10 CH-47 Sea Knight Helicopters,
18x LCM-6 Landing Crafts
Sensors:
SPS-10 - Surface-Search radar
SPS-12 - Air-Search radar
SPN-8 - Carrier Control Approach Radar
I've also added a TACAN - TACtical Air Navigation system

Edit: Added more details, fixed errors

Description
During the cold war but especially in the 1960's and 70's the USN desperately seeking ways to increase and extend it's amphibious assault forces. In that era born the first Amphibious Assault Ships and first helicopter carriers (the conversions of a number of Essex class fleet carriers) and later the true purpose built ship class the Iwo Jimas. These warships were excellent in bringing the troops and their equipment to the beaches and shorelines via helicopters but had two major disadvantages: providing fire support and providing landing ships to carry more heavier and powerful equipment to the battlezone like trucks, half tracks and especially tanks! The United States Marine Corps was always demanded of retaining larger calibre gun armed warships for the fleet to at least provide fire support for the troops in fighting, hence the United States Navy drawn up conversion plans of LPH (Landing Platform Helicopter) type designs for the North Carolina and Iowa classes.
The North Carolina conversion proposal of the early 1960's would had been quite expensive but on the other hand very significant redesign:
The redesigned ships would have carried at least 28 helicopters and 1.880 troops as well as 530tons of troop cargo and 200.000 gallons of gasoline. The armament would had been reduced to 8x2 3"/50 AA guns and the forward most 16" triple turret for trim, that is to balance the added weight around the ship. The cost of such a conversion at that time was estimated almost 31 million dollars!

The conversion of the Iowa class battleships was proposed in late 1961, early 1962 and would had entailed the following modifications:
Troops and helicopter deck would had replaced the aft triple 16"/50 gun turret, all light and all but the forwardmost 5"/38 guns to be removed and one the remaining 16" gun turrets to be modified to fire the Mark 23 or W23 15-20 kiloton yield nuclear shell.
Troop capacity was estimated to be 1.800 men with a landing craft carrying capacity of either 18x LCM-6 or 6x LCM-6 and 6x LCM-8
The Landing crafts would had been handled by two 35ton cranes on each side and they would had been stowed in cradles or davits.
Helicopter capacity was stated to be 30x CH-46 Sea Knights of which 20 could be carried in the Hanger and 10 on the flight deck.
For self defence a single ASROC was to be installed on the nose with an associates SQS-23 sonar for target acquisition.
The feasibility study was created by June showing a raised flight deck aft with crew accommodations directly below it and hanger with a single elevator below that, fuel storage would had been 100tons of aviation gasoline and 675 tons of JP-5 jet fuel. Full storage would amount 650m^2 or 7.000ft^2 of vehicles weighting around 250 tons and 2.800m^3 or 100.000ft^3 of cargo and equipment roughly weighting 1.600tons. For example as a comparison the Iwo Jimas could only carry 1.500 troops and 30x helicopters but no landing craft and thus could not operate in bad weather, even the converted Essex class carriers could only accommodate 1.650 marines and 40 helicopters!
The conversion of the Iowas was quite tempting because the associated cost of such a conversion per ship was stated 65 million dollars while an Essex conversion was 61 million and a new Iwo Jima was 47 million dollars. Not to mention that these ships was fast with a sustained speed of 29,6knots or 55km/h, able to provide heavy gun fire support and carry the same number of helicopters as the LPD, the combined bulk cargo of the CVH and LPD or 64% of the combined troop capacity.
However at this time the USN was facing money issues with much of the allocated founds by the congress went into the large fleet ballistic missile program, ASW modernisation of the fleet and new amphibious construction programs all competing for the same limited founds! Hence this attractive conversion proposal was cancelled soon after.

This drawing too was commissioned by yamato74

The designs had these characteristics:

Dimensions: 262,1m(wl), 270,4m (oa) x 33 x 11m
Displacement: unknown
Engines: 212.000shp General Electric / Westinghouse Steam Turbines, 4 shafts

Speed: 61km/h (33knots)
Range: 27.800km at 28km/h (15000nm at 15knots)
Armour: 178mm, Deck over machinery and magazines, 307mm Belt over machinery and magazines.
Armaments:
2x3 16"/50 (406mm/50) Mark 7 Cannons,
2x2 5"/38 (127mm/38) Mark 12 DP-AA Guns,

1x8 RUR-5 ASROCK ASWM,
20+10 CH-47 Sea Knight Helicopters,
18x LCM-6 Landing Crafts
Sensors:
SPS-10 - Surface-Search radar
SPS-12 - Air-Search radar
SPN-8 - Carrier Control Approach Radar
I've also added a TACAN - TACtical Air Navigation system

Edit: Added more details, fixed errors