Slant 6 with an AX15?

Another option you might look into is grabbing a bellhousing and AX15 out of a Dakota and tracking down one of the 727 adapter plates for a slant 6. I think they used them in trucks.

With that you should be able to bolt up the transmission to a slant 6, but not sure what other problems you would have.

Biggest issue there is how super rare the adapter plates were.