I'm getting ready to put my 6.0l back together, and can't decide what bore size for the head gaskets. The block has 4.010 bore now, with WCCH 317 heads. I don't know if it matters but I will be running a lot of boost if it makes any difference.

 

Im using ls9 head gaskets and the 4.1 bore of the gasket was used to determine compression ratio when I picked out pistons. Dont know if that helps any.

 

LS9 gaskets

 

get a gasket bore that is at least 0.030" bigger than your cylinder bore or your head combustion chamber bore - whichever is bigger.