I would connect the B+ to the ignition switch, so it's powered with key switch on. There is no value in feeding it with live battery power
I would connect the S to the points wire post on the Ignition coil. To me S means signal. Signal is provided by the points "pulse". 4, 6, and 8 cylinder are different, certain resistors are used to make the tach read correctly.
The case should be grounded.
There may be a connection for a light.
