72-93 fleet side Long beds can be converted to short beds with 16 inches of removal,
Cut it about 4 inches behind of the front panel, that way you don't disturb the front bed pocket. you can figure the rest out.

Neat trick we did in the early 90s was to take 81& up 4x2 ramchareger and drop a regular cab on it, leave the back open(except fenders) and make a Mini Big rig.
The ramcharger Wheelbase is 106 inches, a Standard cab and a short bed, needs a ton of work to the front of the bed to work on the 106 WB The rear wheel is about 10 inches away from the back of the cab. so in order to put a short bed on the ramchager frame you have to take out 10-12 inches of the front of the bed,
72-93 SWB Wheel base is 115, Long bed is 131, CC SWB is 133 If I remember correctly CC LWB is 144/146 ?