Wow, thanks for all the replies. There is lots of good info here, but I'm going to let the pros handle this one.
The Sears Micro Extractors worked on seven of the eight bolts, but this last one is just broken off too close to the receiver top for comfort. I don't have a drill press, and a few calls around town have yielded prices of $15.00 - $20.00 for the removal job, so... I'm just going to pay to have it done.
I've learned a some good lessons here:
1.] Get the right tool for the job. The reason that the last bolt broke off is because I originally tried to drill them out, and went too far with this one.
(I knew this rule already, but chose to ignore it...)
2.] This was a Gunbroker deal, and it's not even my rifle, but I won't buy another used rifle without requesting that the scope bases be removed prior to purchase.
3.] Never use permanent Loc-tite™ on screws that you, or someone else, may want to remove one day.