Man - that looks a whole lot like a Astro Hog Bipe [:@]

Blind nuts are pretty easy to dislodge. I use a nail set and a tack hammer (kind of a kid's sized claw hammer - not too much force). The nail set that I use is just fat enough to rest solidly on the blind nut but slender enough NOT to hit the firewall plywood. I give the nail set a crisp tap (not a WHACK) and that's usually enough to unseat the blind nut that has been epoxied in. Then I tap as needed to remove the nut. If the blind nuts are 6-32 (I think that they need a 3/16" hole) I get a dowel the same size, cut it to length so that a bit stands proud of the firewall and glue it in. Flush sand when dry.

Btw, check the alignment of the original mount so that you can recreate the thrust line when you mount the new engine mount.

HTH,