Right Stuff gasket maker

This is what I use...introduced to it several years ago in the aviation industry. Teledyne Continental Motors, came up with it building their engines. Now a Loctite product. Doesn't take set until pressure is applied. Looks and smells like grape jelly. A really good product. I have assembled many engines...no leaks!
646942 TCM GASKET MAKER | Aircraft Spruce

That is for tight machined surfaces only .015 gap as I read. This is the same stuff we used on Cadillac Northstar crankcase's, It is the best I used for tight straight surfaces but wont work on most parts of a Mopar engine.