I have a 1980 300D. Non-Turbo. Has the stock instrument panel with 3 guages/speedo/clock. I also have a new cluster with the tach over the clock on the right side. Any chace this can replace the stock panel? If so, what's needed for the conversion? I have the original parts book that shows no such panel. Bought the car new, but can't remember the story on the tach. Turbo only, maybe? Thanks for your time.

Welcome to THE forum.... You bought it NEW ? That is cool....so you have had it 24 years without a tach.... now you really want a tach.... How did this happen ? LOL

It’s really not so much that I want one. It’s also a curiosity thing. If one of you pros were to tell me it can’t be done, I’d move on with no bad feelings about the issue at all. I was more interested in the idea thinking maybe it’s an easy modification. After 24 years with the car, the fuel gauge started dancing around below half a tank. I cleaned the sending unit, but that didn’t fix it. So, instead of buying a new 3-way cluster for hundreds of dollars, I got the whole panel showing less than 90k on it for $25.00. But, it also has the tach. I know I can pull the 3-way off and solve the fuel issue, because I’ve done it already. Now - looking at the rest of it. I’ve become curious about the tach.
Yep - Being an original owner has it’s perks, so to speak. I think it’s neat to still have every piece of documentation available for buyers of the car at that time. Plus, all the original build and prep sheets, etc. People at the local club meetings think it’s cool to still have the red card that hung from the mirror on a string in the showroom on how (and what) cruise control is. And the tag still wired to the spare on how to use the jack and R&R a tire is a hit, too. Still have all the little booklets and manuals that came with it. The coolest one is the book on locating stations that sell diesel around the US and Canada. (Kind of a joke, these days.)
If you really want something to ponder and laugh about: I decided I wanted a Benz when I was in the 7th grade. I bought this car with cash in July of 1980, two months after graduating high school. My folks put 5k into the pot. The rest came from odd jobs and lots (as in LOTS) of yard mowing. Most of my friends thought I was a freak wanting this car. They all went the American hotrod or truck route. Was it worth all the working weekends? Well - I’ve got a little less than 38,000.00 total into this car, purchase and replacement parts (other than normal wear items of course). That’s about 1600.00 a year/ 135.00 a month to date. Now my daughter Bailey, at age 6, has claimed the car. I honestly think she could be driving it in 10 years. Can any of my friends that though I was nuts make these claims? Many, now still paying on their umpteenth cars? I think not.
I promised myself I'd replace it only when it quit running. Little did I know.........

Check out this link to a question I responded to:

I wish to add a Tacho to my '80 W123 300D

It can be done with the right parts. Also do a search on this site.

Thanks for the info. I'll look into it.