The 190E was available as a 4cyl 2.3 M102 and 6cyl 2.6 M103, both with 4sp AT or 5sp MT. I'm not familiar with the M102 but the M103 wrote the book on needing head gaskets every 100K miles, and early ones came with poor valve guides. A 91-93 2.6 should be out of the woods as far as valve guides.

If a 190E is an option, why not a W202 (C220, C230/K, C280)? Seems to be a lot more car for not a lot more money.

Parts shouldn't be hard to find for the 2.5 turbo. Most of it is a 190E, a bit of it is a 190D 2.5, what little is left is a 90-93 300D 2.5 turbo.

If you're looking for a project, a 190E 2.6 has all the room and fittings to become a 190D 3.0

Sixto
87 300D