If you don't care about saving the pistons (if they're stuck anyway, it sounds like you need a re-bore), just destroy them. Seriously. Take a steel drift/punch, and whack the snot out of the dome, cracking/punching holes in it. Knock the area around the piston pin out, remove the rod, then crack the rest of it. Remove it from the bore in pieces.
Just be careful not to punch anything through the cylinder.
-Brad
