I relocated the tank to the rear frame rails on my '65 short bed step side using an aftermarket passenger car tank. Check out this thread for details.
https://www.stovebolt.com/ubbthread...;Words=filler&Search=true#Post511633Used a stock design repro $195.00 tank from a 1949-52 Chevrolet Passenger Car. The thread lists vendor names for the parts and photos of the installation. I even made a drawing of the tank in the frame.
Hope this helps. Got any questions feel free to ask.