No, early TCC doesn't use any computer signal to lock up. I know there was the switch on the firewall, there was also one hooked to the pedal, so when you hit the brakes it unlocked. Not sure if that one was vacuum or electric.
Just don't cut any wires until you are absolutely positive what it does.
As to the hole in the firewall...if you have ANY idea to swap the truck to fuel injection in the future, I might not weld it shut. Plug it for sure, but welding might be a bad idea. Normally you can undo the grommets by de-pinning the connector and pulling the wires through one at a time. They make a tool for the weatherpack connectors to de-pin them.
Just don't cut any wires until you are absolutely positive what it does.
As to the hole in the firewall...if you have ANY idea to swap the truck to fuel injection in the future, I might not weld it shut. Plug it for sure, but welding might be a bad idea. Normally you can undo the grommets by de-pinning the connector and pulling the wires through one at a time. They make a tool for the weatherpack connectors to de-pin them.
