I don’t know about availability of parts down there or donor vehicles, but if I were building it here there would only be 4 engines I would consider. Any of the 3 455s offered by Buick, Olds or Pontiac or my first choice of a 500 Cadillac.

All four engines make a bunch of low end torque in stock form (and some REALLY impressive numbers can be had with the correct selection of aftermarket components). They are also know for their reliability.

The down side is the BOP and Cadillac share a common bellhousing bolt pattern and it is different than the Chevy BH bolt pattern. I don’t see adaptors for the NV4500 to that pattern but here a link to some posts on what it would take to make it work.

Questions about BOP bellhousings [Archive] - International Full Size Jeep Association

I think it’s doable, but it might take a bit of custom work.

Just my 2 cents.