A 340 Tach question....

FWIW, I have one of the original factory tachs and it works with the mopar electronic ignition or off the MSD tach adapter with the MSD I am currently using. The tach is not powered directly from amp gauge junction, it gets it's power from a switched source. Makes sense that the clock come from that source because you want it running all the time but not for the tach.

The only issue I have with the factory tach is the response is slow. It will not tract the rpm rise like the after market tach I am currently using. It will eventually catch up and the two will read the same.

I plan to rebuild it with one of the new circuit boards RTE this winter.