I have the end bell (completely) off my Hayward SuperPump motor, and have used the trick for stuck through bolts to remove their heads so as to get the motor apart. But my first attempt to unscrew the stump of a bolt out of the bell broke the stump off flush with the bell. I tried (inexpertly) to apply heat to get the stump out, but ... nothing. I previously applied penetrating oil.

What to do? Is it possible to buy a new end bell? Is there a trick to get the thru-bolt stumps out of the aluminum casting?