I've always used some stuff we would refer to as "Gorilla Snot". It's made by 3M. It's actual name is yellow weather strip adhesive or spmething like that. It's yellow and looks like nasal discharge from a Gorilla. Clean with alcohol and keep some cleaner for your hands. It can get everywhere and when it drips, well, it looks like a gorilla was blowing its nose. I'm replacing the gasket weather strips on my '89 GMC RV and it's working just like it always has. Just fine.
Clen the metal and gasket really well, slurp it on, wipe off the drips, use alcohol to clean it from what you don't want it on and let it set up. I think the large tube ran me about $10 more or less. It's in the adhesive/sealant aisle at most auto parts stores. I got my latest tube at O'Reilly's Auto.
