The EMPI Imp construction details are available as measured drawings. It's only two wheel drive; but with an 80" wheelbase, Type II portal axles, a cutting brake and an hydraulic system it would make a passable tractor.
Edit: Here's a Type 181 clone in aluminum:
and as a bonus, here the VW Pingo from Uruguay:
http://jalopnik.com/this-is-the-last-weird-air-cooled-volkswagen-you-never-1790630292
It's a Jason Torchinsky post so we are back on topic.