I can't believe you are anywhere near close on valve clearance with that cam. Even without reliefs.
Do the clay method and check it with the springs you run in place.
Edit: if you do need the .050 gasket there is a Fel Pro gasket that will be just fine. I can't remember the part number but someone here will have it for you.
Also, you need to figure out why the head gasket failed. You are detonating it, the surface finish wasn't correct or something.
