I am putting a rally dash in my car and would like to check the tach befor putting it in and finding out I need to that it back out to get it working. Is there a way to check it? It is a 72 to 74 e body rally dash.

It's easy.

Run a wire from the neg on the coil to the spade lug on the back of the tach.

Run another wire from 12v positive to the long threaded screw on the back of the tach.

Touch the tach itself to ground and have someone start the car.

Done.

Thanks cloneguy,I will try it tomorrow.

Nice cuda collection,I am jealous...

You can also use a tach calibrator like the one RT Engineering sells. Attach the DC connections to a 12V supply and the calibrator to the input.
I had an old one I cobbled from a filament transformer and a capacitor to simulate the engine but due to CRS I cannot remember where it is to tell you how to make it.
Is that a B3 cuda with black vinyl? Mine is B3 with white top and stripe.
Craig