Frozen lower left alternator bolt

I used to go to all the Pick-n-Pull wrecking yards, and one of the things that i used to do was to pull timing covers off the small block engines for resale purposes, when they had 25, 40, 50 % off sales.
Especially 68-69 covers, with the molded in timing marks.
I must have pulled dozens and dozens off donor engines, and also being a professional auto mechanic, earning my living.
At the PNP's i didn't care if a bolt was rusted into the engine block.
I would just twist the bolt head, until the bolt busted in two.
After all, i was just going for the cover, and didn't have to put it back together again.

That small drill hole, and rust bust penetrate, is a good idea.
Never thought of that.
Good idea to try, nothing to loose.

Maybe the op will reply how he finally got everything apart.