There isn't anything behind the passenger right-side kick panel in a W124 -- you're thinking of the 1985 W123 diesel. Behind the battery, a W124 diesel has the EGR brain, which controls the electronic idle (and the tach signal passes through it), the OVP relay, an altitude sensor that talks to the EGR brain, the ABS brain, and the Klima relay for the air conditioning.

I suspect the ABS brains may be the same but the EGR brain is different. You could get along without the electronic idle control if you really have to but it's nice to have. You would have to get that part of the wiring harness out of the car that donated the 603 engine. The OVP relay may or may not be different; the Klima relay definitely is different from gas to diesel.

If I were to undertake such a project, I would want a complete (more or less) W124/OM603 donor car so that I could make comparisons and move parts as I found them to be necessary. There are lots of little "gotcha" items, I bet.

Jeremy

__________________

"Buster" in the '95

Our all-Diesel family
1996 E300D (W210) . .338,000 miles Wife's car
2005 E320 CDI . . 113,000 miles My car
Santa Rosa population 176,762 (2022)
Total. . . . . . . . . . . . 627,762
"Oh lord won't you buy me a Mercedes Benz."
-- Janis Joplin, October 1, 1970