Damn Mopars anyway

Cummins 4Bt would be easier to do than the 6. The 6 cylinder Cummins would be an absolute pain to drive because of the weight. I believe the bare block is 300 pounds.
The Cummins would get good fuel economy.

At least a Cummins comes in a Mopar. Gm engine in a Mopar = fail sandwich.

Yes the 4bt would by far be the easiest to install. Plus in a car you could get upwards of 40mpg depending on how you have it built and tuned, plus you can convert it over to run on used oil which means that if you call major restaurants ahead of time you can have free fuel waiting on you on long road trips.