I was at MIT in El Cajon yesterday. They've been building this Cummins-powered WC-51 for a long time now. It's not a Jeep, but the same could be done with an old Willys pickup, Wagon, or J-truck.

The engine is an old 12-valve B-series Cummins mated to a monster Mercedes-sourced six-speed G56 manual transmission from a newer Cummins-powered Dodge. The frame was stretched slightly and fully boxed. The owner will lengthen the hood and finish the wiring up.