I owned a TR-70 with a Ford engine for several years. In my opinion, the engine was the best part about the machine. It was the only thing we never worked on, and in reality, the TR-70 does not have enough sieve capacity to need the CAT engine, especially with a 6 row cornhead in 150BPA corn. At 2000 hours our combine was completely worn out. Metal was fatigued, bearings were constantly being replaced, the variable speed and transmission clutch were nightmares, the axle housings broke, major and expensive shafts needed replaced, and we took top care of the machine, so poor maintenance was not an issue. It was by far the worst machine we have ever had on our farm. Some plusses were that when it was running it did give the cleanest grain sample of any combine, and the cab was fairly nice and quiet for that age of machine. I would never own another one, even for a second, back-up combine. If you have a dealer close who keeps a good stock of parts you might be OK, as long as you don't run many acres, have a full toolbox, and don't give over $5000 for the combine and heads.