electric motor rpm thru tach?
 

I know someone that is converting an old S10 to an electric motor and he wants to use his tach, because he says the specific motor he is using cannot turn over 6k rpms. Has anyone successfully found a way to do this, and preferably an easy way?

Isn't it just a matter of attaching the pickup to the shaft?

I was hoping their might be an easier way, being that his truck used a Hall effect sensor inside of the distributor.

It might take some testing and calibration, but if he's using the right kind of motor he should be able to measure the back-EMF and correlate that with a rotor speed. Golf carts do this as part of the closed-loop ground speed control.

Beat me to it MEVT!
Does the back-EMF vary with load?
I agree with testing on his specific system. That could give him a picture of his worst-case scenario and he could calibrate to that.