Don't quote me on this but if it's like the OM60X engines, the pistons are of a different design between the turbo and naturally aspirated. On a turbo OM60X engine, the pistons are designed with a built-in cooling duct under the dome. Oil is fed into this duct from the oil jets lower in the crankcase in order to lower piston dome temperatures. I think I heard something like 86 degrees. The naturally aspirated engines do not have this design feature.

That, alone would give me pause for installing a turbo on an engine that wasn't originally designed for one. The earlier post that 617 engines are readily available makes the best sense. By the time you rounded up all the necessary components to boost a non-turbo 617, you'd be farther ahead time and money with picking-up a turbo 617 and dropping it in.

Just my opinion but, I'd have a hard time feeling comfortable with driving for extended periods - always wondering what was overlooked in the conversion and how that would impact long term driveability. Unless you've got deep pockets, it's hard to re-engineer something that was so thoughtfully engineered to begin with; both versions of the 617.

Two thoughts come to mind.

1. In what kind of shape is the remainder of the car?
2. Do you have any attachment to it such that finding a nice turbo 300D like your previous '84 would be out of the question?