I would next try a later W124 diesel such as a 300D 2.5 from the early 90s. My only concern is that those 5-cylinder engines weren't as long as your six so the radiator may be too "fat."

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"Buster" in the '95

Our all-Diesel family
1996 E300D (W210) . .343,000 miles Wife's car
2005 E320 CDI . . 148,000 miles My car
Santa Rosa population 177,300 (2026 projected)
Total. . . . . . . . . . . . 668,300
"Oh lord won't you buy me a Mercedes Benz."
-- Janis Joplin, October 1, 1970