Distributor hold down

I take it this is a slant 6 huh?
If you are real lucky you might be able to coax it out with a small hammer and pointed punch.
If not you are going to have to drill it and use an easy out. (if you don't have a mig welder)
If you do, then lay a nut over it and tack it to whats left of the bolt.
The good news is they are not usually tight in the threads and it may just turn out.