Last time I was in the auto parts store, I started reading all the rtv labels...they all vary greatly in temp resistance, oil contact, sensor safe, etc....
Ultra black, according to the unopened container I'm reading right now has:
Maximum oil resistance
rtv silicone gasket maker
High temp formula--up to 500 F
Not to be used as a personal lubricant.
Assemble parts immediately. Finger tighten, allow to dry for 1 hour, then retighten 1/4-1/2 turn.
Dries in one hour, fully cures in 24.
Don't use it on head gaskets or parts contacting gasoline.
Sounds good to me...I might follow your diy soon...so hope it all works out for you!