Coming through the firewall

Is there a good spot to come through the firewall with the cable from my trans temp gauge? I'm looking for an existing hole. Thanks.

I had to drill to get my amp power cable through because I couldnt find a hole big enough. So I guess it depends on how big the wire is. Why not just run it straight through the floorpan in the trans hump?

When I ran the wires for my fog lights, I made a hole from the inside just under the vacuum booster for the brakes. There was a thin spot in the metal about 2" inches square. If you pull up the carpet by the pedals and remove the bottom panel of the dash you should be able to see it. You can either drill a hole, or if you want the metal is thin enough you can use a punch. Just remember to use a grommit to protect the wire and seal the hole with silicone so you don't get any Carbon Monoxide from the engine compartment.