I finally found a tachometer!
 

I have no idea if it works......not sure which lead is the power , ground or for the coil. The shop manual wiring diagram for my 1959 GMC just shows it going to a sender. What is that? Anyone ever hook one of these vintage instruments up? Says 12 volts on the case. Thanks, -Steve

Re: I finally found a tachometer!
 

I'm that that particular tach if for a bigger GMC.

This is the WRONG one but the concept is going to be the same, the sender takes the signal from the coil and turns it into a signal that the tach understands. https://www.ebay.com/itm/Vintage-Ste...EAAOSwiRNfVYDm

That most likely means that you are looking for a sender designed for the correct number of cylinders.

Re: I finally found a tachometer!
 

Picture of another style tachometer and the "sender" are here: https://67-72chevytrucks.com/vboard/...d.php?t=798290

Maybe the owner is willing to help answer questions?

Using the instructions on the back of the tach in the ad above, I searched for "Sun model EB"

Reasonably priced Model EB transmitter:
https://www.ebay.com/p/1925189234

Instructions for installing Model EB Transmitter. Also includes a simple schematic including pictures of the "mercury cells."
http://toms427impala.info/CT/SunTach.pdf

Found the EB to be 6V using this thread:
https://www.jalopyjournal.com/forum/...e-help.463459/

Searched for Sun Model WB, other driver listed on the back of the tach, and found a reasonably priced tach and driver:
https://www.ebay.com/p/10016142730

And one of just the driver:
https://www.ebay.com/itm/Vintage-NOS...-/303188124330

And finally, here's a company that folks recommend for rebuilding the tach internals using modern components:
https://williamsons.com/


If you're truly up for the DIY experience you might be able to strip the internals out of an older Sun tachometer, one that's new enough it doesn't require an external driver, and use them to drive your current gauge.

Years ago I had a Datsun 240Z with SBC. The tach was "redone" by United Speedometer in CA. It's hard to tell if they are still around. If you want to try, United Radio in NY has been doing GM / Delco repairs for years. https://www.unitedradio.com/

There are a ton of small / local companies around that could probably handle the job as well.

Good luck

Re: I finally found a tachometer!
 

I think Classic Instruments will rebuild vintage tachs with modern internals keeping the original look.