Recommendations for 340 head gaskets and timing chains?

the heads that I Have are 65cc that have been cut 40 with what I believe is the silvolite 1267 piston I would add some pictures or links to parts but I have no idea how to do that . Sorry.
also how do prep the deck of the block for a cometic gasket . I have only use gaskets that are like felpro or over the counter part before. I thought I read something saying that the surface has to be really clean or flat or something of the sort I can remember?