The frame had 16.25" taken out. If you have a short and long bed sitting side by side it's easy to see. There are 8 bolts in either length of bed. The distance between the front bolt and the second bolt will be 16.25" shorter on the short bed. After the frame is shortened, all 8 bed mounts line up correctly.
The new fuel tank is shorter in height so my old fuel sending unit needed a few inches cut off, I am not positive yet if it lets the fuel gauge read correctly, but it should... Could have bought a new sending unit for the short bed style tank instead. There are 2 straps for the fuel tank, the rear one works nice, but the front has nowhere to attach to. My brother made a small crossmember with .25" x 2" wide metal (if I remember right, might have been .375" thick) and it spans the 37" width of the frame and bolts to each side. The front strap had to be lengthened a bit but the tank fits nice. If the truck was 4x4 instead of 2wd, I would have needed to use an F150 tank, excursion tank (where spare tire goes on a truck), or fuel cell. Many people have done the various 4x4 options but I think the short bed tank swap was the easiest and I can fuel up like a factory truck, although I guess the other options would allow a shaved fuel door...