Oh, man Jim! (regards getting the bolt off). No brilliant suggestions but a small story: we'd bought a used BMW 3 series back in the 80s sometime, and I grabbed my under 18 +200 pound (no fat) son to help me break all the wheel nuts loose and then retorque them, just so we'd know we'd be able to change a flat tire. My cheapo 1/2" impact got most of them off; borrowed a Milwaukee 1/2" from a neighbour and got most of the remaining ones off; got out my Craftsman 1/2" breaker bar and put a five ft snipe over the handle for the lost nut, and broke the unbreakable socket. Put the impact socket on, and Dan bounced a bit to break it loose: over a thousand foot pounds of torque on a gosh-durned wheel nut. Soak it with penetrating stuff; get the breaker bar and ft chunk of pipe and a heavy friend. You'll probably also need an 8 ft 2x4 to bolt on some place to hold the engine. Doubt if heat would help here as there's too much metal and perhaps things that would not like to get hot.
Better yet, rent/borrow a healthier 1/2" impact or (even better yet) 3/4". My el cheapo 3/4" drive has handled all my nut busting problems subsequently. Good fortune on this! Doug