The cab will mount differently in the rear.
I bought a 48 for the 5 window cab and decided to keep the frame since the cab fits. The gas tank is under the bed, behind the cab, and the truck has a good passenger side bed side for the tank. The tank looks like I can use it, too.
I have a good 5 window cab from a 53 3100. It needs patch panels (which I have). I just don't care to do all the welding. If you are interested I have it listed in parts for sale.
