Re: Rear eng mount ring bolts frozen
I'd give them some mild heat with MAP gas (hotter than propane), then try again. You need to get some heat on these.
I've had trouble with these, and it's usually that the backside of the heads have corroded to the outer ring.
Ordinarily I'd say twist them until they break, but the nuts are captive in recesses in the flyweel cover (Cast AL). If the bolts are corroded into the nuts instead of the outer ring, you may break the cast AL recesses before you break the bolts, which is not a good idea.
If you can't get them, I've used a dremmel and cold chisel to get the heads off. It's kinda tight in there. Patience is required!
Once the heads are off and you remove the engine/flyweel cover the bolts can usually be turned out of the flywheel cover with your fingers.
Chay