That's a nice stance for that truck.
If I remember correctly, the 2.0 DOHC that came in the Avengers, Eclipses, etc is one of very few engines that can be 90* turned. Those engines aren't too costly, and your D50 trans should
bolt up. That should give you a good FE improvement.
After some searching:
"The Chrysler 904 tranny from an early 80's Ram D50 will bolt right up to a 4G63 motor. This is the same 904 tranny that many Hemi guys run in the NHRA Super Stock class."
I think you'd be looking for the 4G63 motor more than the 420A motor, but it's still a relatively simple swap. Forget carbs, step up to fuel injection!