63-67 have one side-to-side strap; 68-76 have two front-to-rear straps.
Going by memory, the 63-66 have a smaller-diameter filler tube, and the gasket and the tank opening is also smaller, than the 67-up. Otherwise, I believe the 67 is virtually identical to the earlier ones. The strap indentations for the 63-67 are different than 68-up, but at least some of the repro tanks have indentations that will work with either strap setup.
I believe any of them will physically fit up to any A body trunk floor, which is pretty much the same 63-76.