SBC 350, NV4500 out of a chevy, Dana 300 from a jeep with twin sticks and your dodge axles with around 37 inch tires.
That would be a good start. Then as soon as you can get ride of the d44/9.25 set up and go with d60s, d60/14bolt, d60/ford9" combo and some bigger tires! Don't use a NV4500 from a dodge. If you want an auto tranny find any turbo 350, th400 or 700r4. They will bolt to your SBC, they are strong but you will need a good tranny cooler system.

Jeep
Jus' sayin'