Case 188D Crank Nut Stuck

I will ask this question here rather than burying it in my other thread. When I was dismantling my Case 188D, I needed to move the crank to get at the rod bearing nuts. I put the crank nut back on and used a breaker bar to move everything just enough to get a socket onto the bearing retainer nuts. Pistons were rusted into the sleeve bore, so really tight. I neglected to remove the nut when it all went to the machine shop and they left it there too. I'm finally back at this and can't get the nut off the end of the crank. Crank, rod and pistons are in the block. Head is still off. I'm making the assumption that the nut is regular thread, not reversed. I have a fixture made to hold the crank from turning from the flywheel end. The flywheel is still off.

What are my options for getting this loose? I'm not sure if heat is an option but I do have some big cheaters once I know I'm turning it the right direction. Once the nut is off, I am read to put it all together again but don't want to screw this up now...

Tinkerer, Delmer and the other well experienced guys???

Case 188D Crank Nut Stuck