Thanks for the info. I have some friends that are good with a welder if I can get this top end off and studs out of the case!
I was being a little to aggressive with a rubber mallet trying to tap the top end free. That's another problem is the top end is stuck to the case real good. I've been struggling to get the studs for the girdled head out. Have them soaking in wd40 right now and need to get some better flanged nuts to try and get the studs out. I have another engine with the top end I don't care about saving and that one slid right off the studs, that's the way it goes.
Heat is your friend too. Use a propane torch to heat up the aluminum around the threads in the case and the cylinder base holes. It will expand more than the steel stud and relieve some of the tension that the corrosion has created between the steel stud and aluminum castings.
Kroil is awesome. We use it everyday on our big gas turbine bolting that get torqued down to over 18,000 ft lbs. If you also want to make something really slippery you can do a 50/50 mix of acetone and ATF. I use that method for when I press in stuff together with tight or interference fit. Ky ain't got nothing on that mixture hahaha