I have been using pb blaster, but the bolt will not slide out from the lower
mounting of the alternator - 94 civic lx. I can't even move the alt by
hand, so I have been using a prybar and large sledge hammer - then it moves,
but won't free up enough to release the through bolt.

I guess Honda didn't expect the car to be driven in snow and salty roads
when they decided to put the alternator low and next to the front tire when
it will get splashed. It also would have made more sense to use a
serpentine belt instead of 3 separate belts for the accessories.