Inaccurate Tachometer?

[C. Ludwig]

I believe there is a shop that makes a Hall effect speedo drive that swaps in the TII trans. Forget the name. Search on the evil forum. It may work in the NA trans.

The FD and Miata trans senders use a VR sensor. If one swaps to the NA trans it would work with an A/D converter.

There is nothing really better about a Hall sensor. VR sensors generally are preferred for something like wheelspeed where there is a high resolution target. Just need an A/D converter for your gauge and ECU that want to see a square-wave input.