What would be a good choice for applying to sheetmetal (more specifically a custom sump) that will be inside the fuel tank?

por15? something else?

I believe The Eastwood Company has an interior tank coating system, may want to look into that.

There's no reason to paint it and risk having it clog up your fuel system. The original tanks were bare steel inside and they lasted for many years.

Tom

I thought they were galvanized though?

I don't know how you are fabricating it but could you use aluminum or stainless?

LK

keep the tank full and rust is never an issue.

well it will be filled once a week

I cannot weld aluminum or stainless to the bottom of the tank, basically I'm getting a prefabbed piece that is made for low rider trucks to put the license plate in their tailgate...just a box 3 inches deep basically

I will just drill a couple holes in that and weld it down inside the tank, the return line will also feed back into this box

its just to aid in keeping fuel around the pickup