**Gasket or just RTV is the Question**
Red, and stay inside of the studs with it.
1/8 bead and slap her on there wet.
You'll never have even a damp spot.
Contrary to popular belief you can fill it right away if you want to.
I always went with metal to metal and no gasket on surfaces like that
because the gasket material itself can seep a little.
Black is good, red is tougher.