Vickraft,
Do you have a flex joint (5-6" of rubber hose) in the fill line? My concern with your set up is if you get 'tee boned' the fill line could shear off the top of the tank putting raw gas inside the cab making it more dangerous than just having the tank behind the seat.
I'm building a '56 3100 and I'm putting a '56 Suburban tank under the cab. I'm moving the filler pipe to the right rear fender to keep ALL of the gas out of the cab.
Be safe...
Mike B
