Rallye cluster gauge issues - 67 Barracuda
In the fuse box, the accessory feed is the black insulated wire with the flag terminal on the left
The empty slot was used for various optional accessories; tach, rear defroster, air conditioning.
It's not too difficult to get a new or used set of fuse clips and terminals.
You can buy new from Bill Rose - he uses steel ones made by AMP - or used from someone stripping a car. The easiest used ones to incorporate are a set of singles from the accessory slot or the instrument lighting slot (far right in fusebox photo).
Trial fit.
Jumpered from the accessory buss.
if you're only running the tach, the heavy gage wire I used is overkill.
Figured in case some future owner adds A/c or something better to go with the 12 or 14 ga.
For the tach power, I used some blue insulated TXL from Wirebarn.com General purpose wire would be OK too.
Used a marker to put a black stripe on it to reduce confusion with the factory ignition wires.