""There were (are) persistant rumors that the America
was to be a Nuc but was pushed out as a conventional carrier with parts
borrowed from many other decommissioned vessels.""

Not true. the America was always intended to be conventionally powered.

The JFK however was orignally designed to be a nuke. During
construction Robert McNamara, in a cost cutting move, had the JFK
changed to a conventional powered ship.

I served on the JFK in '72 & '73 and the Nimitz in '91. From the Hangar
deck to the flight deck up to the flight deck they are about 85%
identical.