B18C1 head has a small combustion chamber so it's going to raise your compression ratio. It's also a more modern design (the B16A/B18C5 Type R head has been around since '89 I think, the B18C1 only since '94). The only major issue I have with what I've read so far is your buying and engine that's in such bad shape, the guy doesn't want to sell you the orignal head with the motor. If the work is done properly, a new headgasket, new headbolts, the head and block are flush and everything's torqued properly, you shouldn't have a problem, it will be a strong as stock but if the engine's been ragged on and the heads just slapped on, your going have issues, especially witha turbo. I'd consider looking elsewhere for your engine.