If memory serves me correctly I think you have a generator from a J-79 jet engine. I could be wrong but J&H (and the GE equivalent) generators were used on J-47's and J-57 as well.

The manuals from any of the aircraft using these engines will give you the wiring diagrams and the regulator information. These old generators used carbon pile regulators which are still available in surplus stores especially in the Los Angeles area.

J79's were used in the McDonald F-4's. J-57's were used in the North American F100 (I think) and J-47's were used in the North American F86. I'm sure there were other aircraft which used these engines. A copy of Jane's Aircraft of the World could start you toward the information you need.

I think the 750 amp model was used meet the heavy electrical requirements of the Hunter/Killer type of F-4's. As I remember, some of the carbon pile regulators had a schematic printed on the underside showing the wiring to the generator. Some of these generators were also wired to operate as a starter motor.