Sorry, I should give more detail:

I'm retro-fitting a factory tach into a non-tach car, so none of the wiring is there.

It's a '66 factory tach w/ a separate sender like this:



I'm not sure whether M goes to the + or - terminal on the tach - the FSM wiring diagram doesn't indicate this for some reason. I'm assuming it sends the signal to + because that seems intuitively correct, but you know how that goes.

The other thing I'm not totally sure about is which terminal on the tach is + and which is - since one is gold and the other is silver. Is gold usually the +?

Also also, will this work with an ignition system upgraded to electronic? e.g. is the signal at the - side of the coil the same as it would be with a points setup?