One of the weakest points of the inside cab tank is the rubber connection between the tank and filler tube (GM 3691365). Old rubber deteriorates after 40-50 years. Change it out. ****If you smell ANY gas fumes inside the cab, it needs to be investigated ASAP.**** The only side note is that on hot days, with passenger door window down and truck not moving, you may get a whiff from the nearby vented gas cap.

I replaced my tank with a Spectra Premium GM55A (1955 first). Zero gas smell. The PO had used Ethanol gasoline and didn't drive the truck. The Ethanol gas collected moisture and ruined (severe rust) the old tank.

"Adding CFM to a truck will only help at engine speeds you don't want to use."
"I found there was nothing to gain beyond 400 CFM."