What does the 210 722.4 have for a speedo drive? A 722.3 from a 202 might be more easily adapted if there’s such a thing. Maybe a C36 box?

Edit - scratch that. 93-95 300E/E320 (not 2.8) have a first gear start and electronic speedo. Should be as close a match as any.

Sixto
98 E320s sedan and wagon