Check out either the Harbor Freight or Great Northern catalogs. For $1,400 you can get a 20kw generator, the electrical head and the couplings to run it off a tractor pto. At full load these units require about 40 hp but then one usually never runs a gen set at max. These gens could easily be run off a car Diesel engine and I bet any governor assembly from a Diesel welding machine could be adapted to the set.

Check Diesel welding machine repair shops for rigs with burned out gnerators. They often have good engines that could be coupled to the above generators.

I have a 20 kw Yanmar Diesel with a Lima generator for emergency hurricane power-I live on the coast near Corpus Christi. I have a 3,500 sq. ft. house with 8 tons of ac. The gen set will carry all this load and supply my neighbors on either side with power. It uses about 8 gals. a day under half load.