As much as I hate to do it, I will be pulling the original slant6/904 drivetrain in prep for swapping in a 5.9L/904. I use the car as a daily driver, and since my commute is mostly 2 lane desert roads for the 41 mile span, passing is quite important. The anemic power output of the leaning tower of power has become problematic. In addition, I am in the desert, and 115° summer heat and lack of AC makes for sweat-soaked business attire. Adding AC to the slant is very expensive and would further SAP the forward motion generated by the engine. I am keeping the powertrain, and will be rebuilding it with moderately more power (a bit more complression and a bit of cam), but until then, it has to go.
I bought a $400 running, driving '98 Durango as a donor. I'm taking the engine and HVAC and transplanting them into the Challenger. I've seen a few guys get the Dakota/Durango under-dash HVAC boxes to mount up in place of the existing heater box. 2 small holes for the refrigerant lines and some mounting provisions are all that will have to be added. Durango condenser and pump will fit fine as they are. When the slant goes back in later, the HVAC will stay and the only challenge then will be adapting the pump to the slant.