There are always different opinions, but the modern brakes and suspension, gas tank position etc...as mentioned before, all contribute to the positive side.
Im gonna keep searching till I get all of the answers i need before i make a purchase of any frame, but if you buy a longer frame and cut it down, you would then have to cut the drive shaft, and the other area is width...on an art deco a half ton rear axle goes to 59-60 inches on the original frame, so we would have to know the same for the swapped frame rearend, or switch it with a better one.

Much thanks to Bill gervais for sending me those charts and measurements..thanks Bill.