I think a Jeep Wagoneer front axle would be an easy install. Steering might be a bit interesting though. For a frame swap try measuring out an earlier "full size" Jeep pickup complete frame. I think they are "flatter" (not such a big drop in the middle) than the Wagoneer frames and the wheelbase may be closer to what you want. Lots of kits for Chevy V8s to Jeeps.
Good luck and let us know what you do and how it goes!
Ter
