Head question??

So by my calculations a 318 with .030 thick head gaskets and 62cc heads makes around 8.5:1 compression.

The same engine with 72cc heads makes around 7.8:1.

I've heard lots a guys say putting 360 heads on a 318 will drop you compression to 6-6.5:1.

Even 84cc heads make over 7:1!