jcouchster, what Jerry is saying is basically the truth with the C223-T. Not that it's a bad diesel engine, but they had a connecting rod weakness that plagued them after the 200,000 mile mark. If you were to rebuild one today with the most upgraded parts (importantly the con rods), I'm sure it would be better than factory for strength. But as fas as modding one for 115-125 HP, I don't think you could get one to that range without having it be reliable at the same time. The good news is that I think you could see 90-100 HP with a few little mods. Like after upgrading to a little bit bigger turbocharger, better air flow for the intake to the turbo, intercooling the engine, and of course going with a bigger, more free-flowing exhaust. After those mods I could see you easily pushing 90 HP and you really might see the number around 100. Given that gain you're looking at a 20% increase in power with a rating of 100 HP. 80 HP is stock. I know if I had a factory C223-T engine and wanted to upgrade it chances are I'd be satisfied with 90 pretty quick. I'm used to driving low horsepower diesel vehicles all the time and I've never complained. The reliability is what counts the most on these awesome powerplants. It would be cool to see what you could come up with though if you do plan on rebuilding and then modifying. Good luck!

Salvy