I would test run the clock aquired from salvage yard prior to installation for a few days. That almost guarantes it's good. On the otherhand just installing it after removing it from donar car almost guarantees it's bad. Sounds a little like a mechanical movement so a relube may be advisable if access is possible. You pretty well know the last time it was done. :D

Same Technique For '75 450sl ?
 

ALLO.

I have a 450 SL-1975. Same 'R & R' for this model cluster ?

Many tks....