[LH Lead-Foot]

You never know about the guy who answers the phone and says "Parts Department"!
After 30+ years in shops and dealers, I have come across few that know how systems work.
You are getting a quality reproduction tach designed to work with HEI. So, wire to HEI negative terminal, thru grommet, allow extra wire (Unless Included) and attach to the clusters terminal or directly to tach.
I am not familiar with the current offering from Brothers, but you get an 8 cylinder signal to an 8 cylinder tach. I will go and check anyways.

Only in the "LS" generation, the tach signal comes from the PCM and is programmed to produce a 4 cylinder signal. Those who do these swaps can have the PCM reprogrammed or change the switch setting on the back of the tach is so equipped.
Yours is plug and play. Turn the key, smile and go for a drive.