What engine would you build for a Ramcharger?

Back in the late nineties when I was "truck crazy", there was a person with a lengthy web page on all things 70's and 80's Dodge 4X4 and off road. He had an early eighties W150 with a 440 and was pulling down 14 MPG while running 36 inch GroundHawgs. So a lot of things are doable, but I was about to mention something like Sireland67's post, it's a shame that things like usable mid eighties Volkswagon Diesels are not available like they once were, I could stand to drive a Golf for 62 MPG highway mileage. Know a guy that used to hobby around with those, seen it done.