When I replaced my head gasket four years ago, I just let the sprocket rest on the metal support and it was fine. Les' idea of using a zip-tie should work nicely, too. Also, I redecked my head at a machine shop. When I did so, they had to redeck it out of tolence, but I used one of those shims as well. It's held up nicely under a lot of engine punishment since them. As others have said, don't accept that head because of the crack, but (IMHO) don't let the shim be a show-stopper.

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Stay the Trail!