Will an original 47.2/48 under the bed tank fit? Did the 49 frame change from the 48? What about fitting a 48 tank forward of the rear axle on a 54 3100? I have been thinking about moving the gas tank in my 54 3100 out of the cab. I just recently added an underbed spare tire carrier so I would have to put the tank in front of the rear axle where they were located in 47/48.
The early-style 47-48 frame-mount tank should fit your 54, but you'll have to relocate your filler neck and fill the hole in the side of your cab.
I've always assumed that the 47-54 Panel/Suburban side-mount gas tank is the same as the original 47-48 pickup tank. I see them available in reproduction.
