The engine in a 94 350SDL is 606, correct? If i want to replace it with a 300, then I would need to find a donor from a 95 or newer 300, as these are essential y the same engine with different bore, correct? This would be the most straightforward upgrade. To put in a 603 from a 87-94 300 would not be as straightforward, correct?

I might have a line on a "project" upgrade for my '85 300d...if I can get it cheap enough.