[Rwillia4]

I don't think there is much tub sealant left after the engine comes up to temperature. It is only good upto ~350F.

I have used "copper gasket" and had good luck with it.

I believe the true key to getting a good seal is making sure the surface is flat. I have used a standard block and sandpaper. Color the surface with a black sharpie, dand until the black goes away.