suppose your headgasket is blown, it should be assumed that there is also a crack on the head and/or block. should you plan on having the head and block deck milled for that matter, the machine shop should have it it a hot bath, therefor stop leak of any kind should be ok. but make no mistake, you have been warned of its collateral damage. just make sure you diagnose the problem entirely; coolant pressure test, checking for bubbles in the radiator, examining the spark plugs, oil dipstick, engine idle, etc. before you unleash the dog of war!