Diesels are fun. I think you would need somethin pretty powerful to handle the gear ratios you would have on a Jeep though....
Perkins.
We lived off of some crappy gennies in Iraq for about a year before 10 were replaced by two perkins driven gennies. That company's name speaks for itself when it comes to power and overall life and performance. I would pounce on one if I could afford it....

91 Jeep Wrangler YJ, carpet, tires, trailer hitch. yea....