Maybe a Onan emerald 3600 watt generator. Rocketman, who is retired, did an excellent job of putting one under his cargomax at the time, full exhaust, fuel fed from the factory van gas tank, remote start, everything. Serviceability and repairs under there would be difficult, but can be done, and I'd put some kind of frontal cover between the rear axle and the generator to shield it from the rain and snow spray.