Unsticking an unused engine........

Jeff,
I'm in KC and am familiar with the conditions the car sat in. Lots of condensation. I have a 5.9 in the garage that sat in a very similar environment for a decade, and I'm curious if it'll spin.

Rather than pull the heads, I'd like to suggest pulling the oil pan and levering directly on the crank weights, or tapping on the pistons with a piece of wood from underneath. You simply can't get much leverage to break it loose through the crank bolt, as you discovered, and damaging the crank bolt threads is kind of a not-worth-it. The starter has good leverage but not great torque. I've had luck using a pry bar on the ring gear teeth (carefully!) while a buddy bumps the starter, too. Once it goes, it'll probably spin pretty quickly.

I'd give it a run before I pulled heads or planned on boring it. I've brought many many motorcycles back to life after decades of storage, and none of them needed ringed or bored. If it isn't broken, don't fix it. If you run it and the rings ARE bad, you're not going to do any damage that isn't already done.