I just put Moroso valve covers and Moroso rubber gaskets on my 383. I snug 'em down, rotating around a little bit at a time. I hold the ratchet kindda like a screw driver, not by the handle per se so as not to get too much leverage. Snug 'em till I like it. Have never had a problem with leaks. It's all in the feel.

I've done it this way since I was a kid (15 years old in '62) on all kinds of engines and gasket material.

Just sayin'