I'm looking for a donor motor for my 1984 190d 5speed car. I prefer the turbo motor but for the right money I may be interested in the naturally aspirated 2.5. What class is this motor?

It's the OM602. I don't know if that's the class, though. There are 3 basic variations of 602 in the US that I know of. The normally aspirated 602 in the 190D 2.5 (86-89), the early turbocharged 602 in the 190D 2.5t (87-89) and the later turbocharged 602 in the 300D 2.5 (90-93). The later turbocharged 602 has more electronics controlling the IP and boost control and it's not an easy thing to disable EGR... if you're of that ilk.

Is it a simple matter to drop a 602 in place of a 601? I've read that there are differences in the engine bays of the 4cyl and 6cyl gas 190Es making it difficult to drop a 103 in place of a 102. I wonder if the 5cyl 190Ds use the 2.6 engine bay.

Sixto
91 300SE
87 300SDL
83 300SD

Was informed on another post that the 190D 2.5t was only sold in the US in 87.

Sixto
91 300SE
87 300SDL
83 300SD

Thanks for the info that just what I was looking for.