What is the best sealer to use on gas tanks? This is actually a truck application but I need something to seal the in tank fuel pump housing.
Is Blue RTV gas resistant?

DO NOT use any kind of rtv for constant exsposure to gasoline. I'm not sure what exactly your trying to do but most intank fuel pump housings snap together and use orings on actual pressure connections and suction screens,Smitty

Its actually the seal on the top of the tank where the lines come out. Its basicly a round plate on top of the tank. I'm looking for the best product that is gas resistant to seal it. Its a 4x4 and leaks when subjected to sloshing and extreme angles.
The stock gasket leaks and I'd like to glue it shut with something substantial.

Dow Corning 730

Not cheap but it is gas proof.

Try www.mcmaster.com

730 Solvent Resistant— Contains fluorosilicone rubber, which resists swelling when exposed to fuel, oil, and most solvents. Nonrunning paste for repairing fuel lines and tanks, bonding components exposed to solvents, and making formed-in-place gaskets. May corrode certain metals (including copper, brass, zinc, and carbon steel). Begins to harden in 25 minutes. Temperature range is -85° to +400° F.

Or aircraft sulfide cured compounds. Two part sealer sold underthe name PRC Proseal. This is the stuff used on wet wings and is Jet fuel and 100LL resistant. I can't comment about how it would hold up to todays aromatic laced fuel but MEK has very litle effect on it.