Good luck on the cheap part. I can remember not so long ago when they could be picked up for a song. It is not that way now. S99&#039;s would had been an excellent investment 10 years ago, as they have appreciated more than most other investments. You might look into getting a S99 GM if that is what you want one for. You can use off the shelf parts readily available from any Detroit Diesel dealer to boost the horsepower considerably. The 3-71 is still available, and often can be found brand new from government surplus, plus, they were used in many applications, industrial, construction, mining, municipal, military, etc. There is no parts shortage for that engine.