I put the receiver in a vice, wrapped in heavy leather. The 1/2" round bar is a perfect fit in the hole in the trigger block.
I figured it this way: The gun wasn't any use as it was, so I really didn't have anything to lose, so I just reefed on it. It's not so much spring pressure you are fighting, but corrosion caused by years of dissimilar metals being in direct contact.
I think we're all Bozos on this bus.