Okay I found a set of nonmilled (stock cc) perimeter bolt LS1 heads that I would like to use on my 5.3 motor.

The 5.3 is 9.5:1 comp stock w/ ~61cc heads. These heads are ~67cc I want to use. I read that I need a certain headgasket for the older heads for the coolant ports to line up too.

So what is it going to take to use the perimeter bolt heads on my 5.3 motor?

I'd like to keep my compression around 9.5:1-10:1 on the 5.3 motor also. Would I need a thinnner headgasket and to mill the heads to achieve my desired compression ratio? Can the LS1 heads be milled .030-.050 safely?

I am lost when it comes to adapting these heads...