The vehicle in post 67 has a Cummins 4BTA 3.9. It is the same basic engine as the 6 used in the early Dodge trucks but came out of a timberjack skidder. Lots of parts interchange and it weighs 200 pounds less. Lots of guys who redo old power wagons have used this engine, and it was pretty common in boats where it could get around 250 HP. It took some thinking to get in and tractable, since it is a 2800 rpm engine, but will do 70MPH loafing at 1800 RPM at max engine torque in 5th high range, and 3 MPH at max engine torque in first low range. I haven't been visited the site for a while, but there was an entire interweb forum devoted to conversions.
Ron