Want to put and aftermarket tach in a rallye dash

The way i wired up my IVR i used red as 12V feed, yellow as the 5V output, and black as ground. I used ring terminals and pulled the 12v feed directly from the stud that fed it into the gage, and ditto with the 6V output from the fuel gage. When i converted to volts i enlarged the holes in the gage housing and fit plastic grommets, then used plastic spacers and washers to insulate it from ground shorts. I ran a red positive lead to the 12v feed stud at fuel gage, and a negative ground to the cluster housing. Later on i ditched the volt gage negative ground wire, and ditched the insulators on the negative side of the volt gage. I just stacked up steel washers and a nut to ground the negative volt gage stud directly to the gage housing. Doing it all this way eliminates extra wires everywhere and keeps nothing but stock plugs in the cluster.

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