Got the replacement head cleaned up and ready to install. Gasket showed up a few hours ago. Found a NOS OMC gasket that retails for $42, on ebay for $13! Today smacked the bolt heads a few times with a drift pin and a ball peen and then soaked them with PBB. I can't imagine much if any making it down to the actual threads though.
Going to try to get the head off tomorrow. I'd apply some heat if thought it would do any good. Those threads are pretty well protected under the gasket it seems. Heating up the entire power head with a torch seems a bit futile. Wouldn't the alum just act like a big heat sink and bleed the heat away right quickly? I only have a medium size torch set. Not a big one like a real shop has.