The speedometer on my '80 300SD is shot. It only works if you slap the top of the dash, and the odometer and tripodometer have never worked since I installed it about a year or so ago. I have found a complete cluster for a '79. The part # on the face of the speedometer is different, and it registers 120MPH as opposed to the 85MPH on my 1980. Does anyone here know if the wiring plug ins and the speedo would work if I switch to the new cluster?

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1980 300SD 146K miles.