Being the first diesel v8 in a car, is there not a way to make these run well? Or is it the fact its a gasser turned diesel and can’t handle it that makes them rough?
It's not quite just a gas engine turned diesel, but close:
Contrary to what some believe, the Olds diesel was not just a gas engine "converted" to a diesel; the block was of similar dimensions because using the same bore and stroke meant Oldsmobile could build the engines using the same tooling as the gassers. The block was a beefed-up design intended to deal with the engine’s 22.5:1 compression ratio, which was nearly 3 times the CR of contemporary gas engines.
Unfortunately, one thing Oldsmobile didn’t change was the head bolts — type, pattern and number. And that would prove to be the engine’s undoing … or at least part of it.
https://www.autotrader.com/car-news/when-diesel-was-dreadful-oldsmobile-diesels-259997