So - the Dart project is at a crossroads. Might as well contemplate other engine options.

I have a postal jeep 904 automatic with a Chevy bolt pattern on the front, or a /6 727, if either of those opens up options for you. 

Going off the reservation a little but a Lincoln LS 3l v6 with the manual. Add boost to tast. 

Pentastar v6 with turbos. If you can find a ZF 8 speed 2wd auto, they're fantastic. Otherwise I recall some parts bin swapping with a wranglers clutch bits and bell, and the 6 speed from a crossfire.