Check into Onan residential generators. They have Cummins motors in them and are extremely reliable. I've come across a lot of them lately, and talking to the home owners, they've all been very pleased with them. Probably pretty pricey tho!
The residential air cooled standby Cummins-Onan generators I checked out were either powered by Briggs and Stratton or Subaru-Robin, depending on the size. I have an air cooled Kohler 20kw LP gas powered residential standby generator.
Bill