Tach and Spedo compatibility with 1980 GS850

So I have a 1980 Suzuki GS850 and the tack cable went. No problem, lots of them out there, replaced. My issue is the tack itself. Now that I am sensitive to the issue, I can hear it "grinding". Sometimes the grinding stops and starts, but it is definitely there in the Tach.

My question is is the cable connects and the Rpm's and the wheel speed of the GS1000 of the same vintage compatible. I am not worried about the mounting or the electrics. I am only concerned about connecting them and having them read somewhat accurately.

I am asking this because there are generally NO GS850 ones used I can find so far. One new one for $1500 US, not gonna happen. But I do see a lot of GS1000 used ones out there for reasonable prices.

Will they fit and read right? I can do all the mount adjustments with no problem.

Any help in any direction would be appreciated.

Are you married to the idea of an OEM look or would you also consider some aftermarket options?

Aftermarket would be fine.

Have you considered going electronic? I have a couple of Trailtech Vapor units going on my CB750 and CJ360.

I would not mind electronic. are they available at TRail tech?

I think Trailtech is only a wholesaler. I got mine from a local shop. eBay should have them, too, but I haven't checked.

Sonreir, how do you like them? I've been debating on using one. Nice thing is that you don't have to crack into the harness right? Magnet for speedo, induction for RPM and ring under the plug for temp?

Also, don't mean to thread jack...we were kinda on that topic

Installing it onto my drum brake was a bit of a chore, but other than it's pretty decent for a universal solution.