A 12A can be had pretty cheap used, if its blown sometimes people damn near give them away. So find yourself a nice cheap 12A and tear it down. Clean off all the parts, and grab a FSM so you can see whats in spec (reusable) and whats out of spec (garbage/ paperweights)

If you've got the money though, I'd suggest buying new rotor housings, they're usually about 400 a pop, but they'll ensure the highest possible compression. A depending on the condition of the other internal parts you'll need new seals and springs. A full rebuild kit from Atkins Rotary is about 1k but if a good number of parts from the original motor can be reused, you'll spend much less. Regardless though, all the soft seals need to be replaced.

Sounds like you're pretty handy w/ the tools, so I'm sure you can figure out a way to mount it, cuz if not that will be expensive.

Another option would be to send it to Rotary Resurection that guy does rebuilds starting @ 1k. Anything from the basic econo-build to port jobs and completely new components.