What to use to seal the fuel pump/tank?

[hockeydad4-22]

I cut the access hole for the fuel pump in the tank, the used 1/8" bar stock to make back up plates, cut the access hole in the section I removed and then put the whole think back in the tank. Now I have to make the cover ring and screw it down, sandwiching the pump flange and locking it in place.

Now the question, what would you recommend to seal everything? RTV? Something else?

Thanks

[Gunnibronco]

When I went to the car parts store asking about sending unit oring, they recommended Right Stuff. He said a lot of mechanics are using it instead of a gasket when sealing sending units. I haven't tried it, but when I put my tank together, I think I'm going to use the oring with a little Right Stuff for good measure.