I asked for this info numerous times on moparts during the past year and no one came up with it. I've got it figured out now, and thought I'd post it here for all the rest of you that didn't know the answer.

On 1970 E bodies, The hole that is made in the firewall for either the 4 speed Reverse light wiring OR the Cruise control wiring (both use the same hole) measures .75 inch diameter. This is for 1970 cars only. (different grommet than the 71-74 cars)

(of coarse, if you're not using the factory grommet, you should match your hole to whatever grommet you're using.)

Tav

Nice diagram, but could you make it larger so we can more clearly read it?

My '70 Challenger 4-speed has the dash-mounted reverse light hole where the cuda roadlamp hole is in the pic. And where the pic has the dash-mounted reverse light hole, mine is just dimpled. Factory error I guess.

Challenger vs. Barracuda use different locations as do 1970 vs. 1971

Hi Dan. Could you explain a little more about that? So I should use the roadlamp hole for my 70 Challenger cruise wiring then?

Thanks
Tav

Thanks for the better pic Snoopy. The 1970 Cuda label helps also.

Does anyone have more info on this hole being different on challenger vs cuda?

My 70 challenger firewall (SPD 8-26-69) has a big dimple at the spot marked reverse light, and a small dimple at the spot marked roadlamp. I need to know which one to drill out to .75 inch for my grommet. Why would the location differ on challenger vs cuda when they used the same wiring harnesses? Seems like that would just confuse the line workers.

Tav

There might also be a difference between LA and Hamtramck built cars.

It really shouldn't be that hard to figure out. There ought to be plenty of people with 4 speeds here on moparts. We just need a few of them to take the firewall picture in this thread out to their car for comparison and come back to let us know what they found.

We need to know location of a...
70 Hamtramck Challenger 4 speed firewall hole
70 LA Challenger 4 speed firewall hole
71 Challenger 4 speed firewall hole

No measuring required. Just tell us which spot from the picture in this thread was drilled out on Your car.

Thanks
Tav

My dash mounted reverse light hole is where the roadlamp cuda hole is in the above pic. My car is a Hamtramck built car.

Thank You!

2 more to go...

Tav

My 1971 Challenger 4 speed car has some differences from the picture that Snoopy posted for a 1970 Cuda. The location that is shown on the 1970 Cuda for the two holes for reverse light and cruise control,my car only has small dimples in the metal. In other words I do not have any of the said holes between the bulk head and brakes. My reverse light wiring comes in to the engine compartment below the throttle cable and above the gas pedal.

Thank You!

Along with the relocation, I'm pretty sure the 71-74 cars used a different grommet/hole diameter than the 70 cars.

1 more to go, 70 LA Challenger 4 speed.

Tav

70 reverse on the left uses 3/4 inch diameter grommet/hole.... 71 up on the right is 1 inch.

I found this on a reverse light housing I bought a long time ago at the Spring Fling. Has anyone seen one of these and what models used them?

Dash = 3/4"

Thanks for posting that pic mccannix. I've had that pic in mind since I started this thread.

Tav

So we've pretty well established that the 70 barracuda firewall hole locations are different from the 70 challenger locations, and that the 71 challenger locations are different from the 70 challenger locations. It makes me wonder if the 71 barracuda locations are the same as the 71 challenger or different. Anyone know?

That 70 Cuda firewall pic is really excellent. I'm thinking it would be great to have a similar pic for 70 Challenger & 71 Cuda/Challenger. My firewall doesn't make a good example or I'd take a pic of it. If anyone out there can post a pic of one of these firewalls here then maybe we can get some labels put on it for all of us to use as a reference.

Any 70 Challenger or 71 Cuda/Challenger firewalls out there available for picture taking?

72,73,74 firewalls could be educational too. Don't feel left out, post em if ya got em.

Thanks again to all.
Tav