I have a pair of 400 heads (76cc) I am putting on a 350 I am rebuilding. My question is I want to mill the heads down but I am not sure how much is too much. Okay i know what your gonna ask and the answers are; flattop pistons (8.33 comp. rat. 76cc heads) and I am hoping to get close to about 9.25:1. I will be putting on the .016 head gasket to help. I would appreciate any help.