Thanks for all the suggestions, much appreciated. Yeah, I don't have torches or welders here. Just a bunch of craftman hand tools, etc.
From some internet research, it sounds like a "carbide burr" might work - they are expensive drill bit like things.
Also there is something called the "rescue bit" made for this situation. Also not cheap at $53 + shipping I assume
https://rescuebit.com/
I would just take the manifold off, since I've already got an engine crane setup to lift the motor and pull the oil pan - but I'm worried I might break off a manifold bolt in the head, and then I'd be really up sheit creek. I already tried to remove the heat collector (for air cleaner) and just those bolts are very rusted solid. Started stripping one with a 12 point open end
Quite a dilemma - and I haven't pulled the old rear seal with the crank installed using the "sneaky pete" tool yet.