I know its too late now, but you could have pulled the head with intake and exhaust manifolds in place. Be carefull to remove the head by losening the head bolts in reverse order from the tightening pattern. The head gasket must be allowed to seal under a no pressure environment. So when you are ready to start the engine, do it without replacing the radiator cap. Allow the engine to run for 10-15 minutes at operating temperature while the sealant printed onto the new head gasket melts.