Don't know if it will work with a GX head though.
My second spare GX head was machined to the max by the previous owner due to warpage.I thought about grinding the one chamber a little to get the cc's equal as everyone was 10,5 : 1 except the last one that was 11 : 1. I could see it had some detonation marks on the valve heads.
I talked to a cylinder heads specialist and he said there is not enough meat to do it.