Thin head gaskets???

thank you all for the info .just what i needed to know im going with SCE pro copper .021 they are a hundred and eight bucks but i believe they are quality gaskets for my 1974 360 with 2.02 j heads.will be running a comp cam high energy cam 2.68-280-.477-.480 cam.would like to get whatever comp gain i can without changing pistons getting them from summit racing.ive always ran the mopar .40 compressed.expensive but as the saying goes ya get what ya pay for.