To 97SL320 and tecqboy,

Thank you for your comments and advice. I finally got into the Mercedes On-line parts catalog, and found that the 129 540 71 48 is currently listed as the replacement panel for my '91 300SL. So, I cabled it, tried it and everything works! Speedometer and tachometer appear to be properly calibrated. Resetting the Electronic Odometer will probably require a Mercedes shop.

Thanks again, Bob Deming