keep in mind a suburban gastank will fit between the rear rails(if yours are still stock) and is 42 gal nad if you get the right one(yrmodle) out of the junk yard you can you use stock sending unit and pump so youll have a gauge and no for damn sur eitll work.
i have a guy here in texas that is building me 36 gallon fuel cell theat fits rear part of the frame for $425 i have to pay an extra $225 for adjustable fuel sending unit ......................talk to the fuelcell guy at 903 569 8949 or 903-571-5125
my truck has an 80 gallon in it right now, yes I said 80 gallon lol.
But during the rebuild I'm picking up a spun aluminum 20 gallon hot rod style tank, and putting it in the bed. I think 20 gallons is enough, for me atleast.
I thought the fuel cell guy went out of buisness or something, at least his web page was dead. I havn't looked lately, but that was 6 mouths or so ago.