Tach Wire Through Firewall

[70 Challenger Lover]

Is this red arrow where the grey tach wire passes through on a 71? Didn't see it on the body hole schematics or in searches.

I was going to do the gauge conversion to rallye gauges based on Roadman's instructions but he has it going though an unused spot on the bulkhead connector. I have AC and it doesn't appear I have an unused spot.

Just want to be cautious before drilling holes.

[MoparCarGuy]

The tachometer GRAY with BLACK or RED tracer wire goes through the bulkhead connector at location 20. It may change to Gray with no tracer or still have a BLACK or RED tracer as it makes it way to the tachometer stud. The DARK BLUE wire is the ground wire for the tachometer.

FWIW, a vast amount of info on body and firewall holes is in this thread. https://forum.e-bodies.org/reference-material/18/e-body-hole-locations-firewall-door-interior-ect/303/
I did not see that hole labeled except on a Cuda firewall. It was the Cuda Road Lamp power wire with grommet.

[MoparCarGuy]

This 1970 Challenger wiring diagram is very useful as it is color-coded. You can see the gray wire from the coil to bulkhead #20 and on to the tachometer.
FYI - That 18DBL (DARK BLUE) wire provides ground for a lot of other accessories including the tachometer.

[70 Challenger Lover]

In looking over my harness again, I realized that I used hole #20 to run a wire to the electric choke. Guess I can undo that.

I dug through some reference pics from my 70 Challenger and found something in that same general area. The car was completely original when I got it. It's a grey wire with a heavy rubber grommet fused to the wire similar to the license plate light wire.

[MoparCarGuy]

That appears to be the Reverse Light wiring for a 4-speed car. It goes to the dash reverse light between the ashtray and the glovebox.

[70 Challenger Lover]

Okay, that makes sense. It is a four speed car but still apart so I had forgotten. Thanks!