Hey man I just barely did my crank out of the engine. It was a real pain in the ass because the impact was almost not strong enough.
First, go to your local autoparts store.
Second, purchase the lubricant that freezes while lubricating. Stuff is the shit, military friend says the army switched to using it on all there stuff so it has to be the goods when used for working on tanks, planes, and the like. It freezes the threads while lubricated them, causing them to shrink and break the rust that is keeping the bold fused.
Third spray it real good. Keep in mind it has a really thick washer that you need to get behing to hit the threads, spray there for a real long time. Then hit the back behind the crank pulley. Let it sit for about one minute.
Turn your impact as high as it will go or whatever you've got(I used a somewhat decent 1/2 inch impact) and drill it for a long time. Slowly it will, all and all, jar loose a bit then quickly come off.
Repeat as necessary.
Let me know