So, 94 3.8L V6 Mustang, originally the thermostat was sticking and it was recommended it remains in place till replaced. It wasn't and overheated and stalled out on the guy, when I got to it; all six plugs were fouled with oil, gas and water. Same mixture was seeping out of throttle body. When plugs were cleaned and engine was managed to be turned over, white smoke poured from the tailpipe. I'm sure it's a head gasket, but my main problem is that both bolts on the thermostat housing/water outlet, have rusted into the intake body and the heads have sheared off. I can't seem to find the bolt sizes to save my life so I can drill them out and either rethread or stick a helicoil in it. Would anyone on here have any idea on the answer I'm seeking?