I made a one-time racehorse deal on 8 retired UPS engines, with a buddy who was a shop foreman for UPS. I got 7 running engines, and one without a cylinder head. (I paid just about scrap iron price for running engines!) They're 120 HP turbo diesels, about the size of a 292 Chevy, but somewhat heavier. I dynoed one, and it makes its rated horsepower, 120 @ 3600 RPM. I've got 5 running engines left, and the parts engine. They were made by Onan as power generator engines, and when Cummins bought Onan, they sold them to UPS as delivery van engines. The UPS demand exceeded Cummins' ability to supply spares, so they retro-fitted to a different engine. These engines were used interchangeably with 292's and F*rd 300's, so a van could be converted from gas to Diesel with just a fuel change. They're set up for Chevy V8/292 bellhousings, with the old hydraulic-clutch bellhousing with the throwout fork on the passenger's side. They're equipped with a 12" Chevy clutch, and any Chevy-pattern trans will bolt up. I've got a New Process 235 4-speed to use on this project, but I'm searching for a 5-speed Clark with 5th. gear overdrive, with a Chevy bellhousing bolt pattern. No luck on the wheels, as my contact man retired a couple of years ago!
I've got a line on a couple of wrecker beds, with PTO-driven winches, or I might fabricate my own bed and booms, and use a PTO winch. I ran a wrecker service for a while, and did most of my own maintenence, and even built a few special-purpose beds and rigging. This project is way down the "to-do" list, so I'm not locked into a final design yet.
Jerry