92 Grand Am engine mount

[GrandAmNot]

92 Grand Am, 4-door, 2.3 L SOHC, 58,000 miles.
Going after the head gasket. Manifolds removed. That extra exhaust manifold support bracket was a stubborn surprise. Removed the half of the engine mount attached to the wheelwell and the 4-bolt L-shaped aluminium part(the dogbone?). Can't get the plate off that's attached to the side of the engine. Four bolts from the mount to the plate and three bolts through the plate to the engine block. Need that plate off to get at timing chain cover.
Have used WD-40, Liquid Wrench and the closed end of a 15mm wrench and a pipe extension but those three bolts won't budge. Do I need heat? Would a Benz-o-Matic be hot enough? Are those bolts reverse threaded? Have already just slightly rounded one bolt head. Any more of that and the project is over. If its not just the head gasket the project is over.
A used or rebuilt engin is not an option$
Tempted to drill holes in the wheelwell and use a break bar and socket.
Thanks for any ideas or suggestions. Keith

Sorry. Thought that first post didn't go through. Something about logging in and thought I had to start over.