Swapping frames is 99% of the time a total loser. There are so many add on suspension componants to make your truck ride and drive better it just makes more sense to keep the original. It may be cheaper, but there is SOOOOOOO much time needed to modify EVERYTHING it just isn't worth it.
You will see people asking about frame swaps with the only thing on there mind is the wheel base. That is JUST the begining, and in fact the EASIEST thing to change. Heck, you could have a frame that had a foot longer wheel base that shortening it would be MUCH easier than using another frame that may need many more mods but the wheel base is correct.
The inner fenders and rad support would need SERIOUS mods to use just about any other frame as an example. The steering column location would need to be modified, the motor would be too far forword on the later truck so that would need to be changed. The frame on the 50 is VERY narrow, the later frame would likely get in the way of all the bottoms of the fenders and running board aprons.
All new running board brackets would need to fabbed. The gas tank location woudl likely need to be changed.
The list goes on and on.