Definitely a B18 head. Valve sizes match, combustion chamber sizes match, casting in the right place (thanks - that's new to me).

I've got a B20 head and block laying around from when I purchased another Volvo guy's stash when he moved from town, I just need to unearth them. My thought was to keep it original, but plans change.

Just out of curiosity, I thought that the B18 to B20 overbore was fairly common and left sufficient meat around the cylinders. Is it the fact that they need to go another .020 over to clean up the bores that jeopardizes the project or just the thought that I should start from the strongest position possible?

Thanks for everyone's advice!