KEITH - Best place for Right Stuff IMO is on the end gaskets of V-8 & V-6 engines where the bottom of the intake mnifold tries to seal against the block. Most gasket kits include CORK gaskets. First thing I do is THROW THEM AWAY. Run a large bead, about 1/4" dia of RS across the top of the block, let it set up a bit, drop the intake on and NO LEAKS.
IH truck dealers sell tubes of a gray sealer for sealing up the Powerstroke diesel engines, things like timing covers, oil pans, etc. I've never actually heard who makes it but I think it's RS in a different package. I will say this about IH's PSD, they used formed o-rings in many many places, they really don't leak much.
The hardest thing I ever had to seal was our glow fuel powered RC engines. If the nitro in the fuel didn't attack the sealer the alcohol in the fuel did, and the blend of oils in the fuel made everything a mess. Permatex aviation form-a-gasket would last maybe two weeks on them. Finally started using the red high temp RTV very sparingly and that seemed to stop the vacuum leaks.