Engine is out and I'm knee-deep into converting from carb to TPI. Using an Innovate LM-1 kit and planning to mount the sensor in the tube that PO replaced the catalytic converter with. I was going to drill a hole sized to the cable and run a pass-thru near where the ECM wiring goes, but now see that the plug on the end of the cable won't allow a tight fit through a grommet.

How have others gone into the cabin?

Here are pics for a bit better description...

Plug that connects to the command module inside the cabin. Larger than the cable diameter.

Had planned to go through this area with a hole and grommet, similar to the amplifier power wire that is above the ECU plug.

 

How long is your cable? I think, I routed mine along back of firewall, (top of it), to passenger door, and maybe under the seal, and then down under the dash. I have a very old LM1, large box, and I have it mounted to the right of the steering wheel, on dash.

 

I think I have an 8' cable. Spent this morning working on the wideband solution. I decided to go in through the HVAC grommet, had to slice it and remove a small chunk for the cable to go through and still allow the grommet to seat fully. Used a bit of spare silicone caulk to seal it back up.

Not sure if this route would be accessible with the engine in place, as it is pretty far down in there!

 

You can get large OD with small ID grommets for just such an occurrence, or hole plugs where you can cut your own hole into, for future reference

 

I followed the factory routing for the ECM wiring (ECM is long gone).
From the engine bay, over the passenger side inner fender, behind the fender itself and into the cabin through the large grommeted opening in the door jamb. You end up behind the kick panel.