Repair of crank cap threads is difficult at best. Minor cross threadings can be picked at and
repaired, major ones, better to just get a new crank.

eg: Components - Drive Train - Cranks - Crank Arms - Left-Side Crank Arms - Page 1 - Niagara Cycle
$12 for compatible arm. Assumes not hi-zoot arm in first place.

For another $25 or so you could get a cartridge BB.
Doubt the Jacobs taper wedges referenced would work as they are well under 1/2" in their opening. Also drill chucks on their tapers
have a very small gap in which to work, but do need a gap. If the gap is too big or too small....
Here is wiki on JT taper sizes, you would need one for a #2 1/2 or #3 JT. eg: http://www.shars.com/3-wedge-sets-for-chuck-3jt-2-1-1
https://en.wikipedia.org/wiki/Machine_taper