If the flutes on the tap aren't plugged with material, a tap extractor tool might work. A tool with fingers that go inside the flutes of the tap to back it out of the hole.
Similar to THIS.
The worst that can happen is the finger on the tool break off in the tap flutes.

Kevin
1951 Chevy 3100 work truck
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1929 Ford pickup restored from the ground up. | 1929 Ford Special Coupe (First car)
Busting rust since the mid-60's
If you're smart enough to take it apart, you darn well better be smart enough to put it back together.