I used a 1/2" titanium bit and drilled through the frame, then used a cut off disk to widen the holes a little so I could get a wrench in to hold the bolt while I tightened it. I used M10-1.25 35mm bolts and M10-1.25 nuts with flat washers and locking washers.
Here's a pic of the newly installed mount before I cleaned/primed/undercoated the whole area:
The car drives a whole lot better now. No more engine jumping.