Best gaskets for 340

Ditto ^^^^

I have also used Mr. Gasket , Detroit baskets and MP as well with excellent results.
Really the key is clean surfaces, proper installation and torque applied in sequence.

The only thing about gasket kits is the often unknown head gasket specs. That bothers the crap out of me. Sometimes you need a certain size for a reason. Like zero deck pistons and closed chambered heads.