Bill,

Sounds like the last pump replacer didn't use anti-seize on the pump bolts. 
 This is a must for bolts on aluminum engines.  I suspect that when you get 
the bolts out, they'll take the threads along with them.

In any case, the water pump is not a small job.  I just did mine on 
Saturday expecting to take about 4 hours.  I spent about 6 hours actual and 
8 hours elapsed.  And, my Allen head bolts came out OK.

Mike