Is it a four speed manual presently? If it is and you have the pedals and you don't want to use the Hemi I would think about this. Find a low mile Magnum NV combo. A Magnum has a very similar hp and torque curve up to 3500 rpm which is perfect for a truck.Bolt right in.

2021 Dodge 2500 4WD Cummins
2020 Challenger R/T Scat Widebody
2007 Charger R/T 5.7