The 1/2 panel-body fuel-tank was 16 gal for all Advance-Design years and 18 gal on 1 ton panel-body trucks for all Advance-Design years.
As might be expected, the early A-D standard-cab trucks with between-the-frame gas-tanks had fuel capacity of 16 gal (for 1/2 and 3/4 ton) and 18 gal (for 1 ton). When the fuel tank went inside the cab, the fuel capacity reduced to 17.5 gallons.
As best as I can recall, the filler necks lined up OK when I restored my Suburban. I think I left the straps a little loose until every thing was lined up.
