[mr48chev]

I wouldn't fuss with the electrical side, that can be circumnavigated too easy.

Back about 25 years ago I bought a 64 GMC from my buddy who had taken it in trade from someone else. I could fill the float bowl and it would fire right up but wouldn't pick up gas out of the tank, I went and got gas for it and fussed with it for a day or more until I decided to get under the truck and trace the fuel line from the 35 gallon stainless tank in the bed to the fuel pump. Right under the seat was a 3 way manual fuel valve like we used to use with auxillary tanks on trucks back in the 60's and early 70's before the square body trucks with dual tanks and the electric switch. It was turned to off.

It's easy enough to cut the ignition wire from the switch to the coil and add some wire and a hidden but reachable switch. Trouble is that a jumper wire with a pair of alligator clips under the hood bypasses that and it is too easy to bypass the starter switch. Shut off the fuel and they aren't going to drive it away especially if let it idle and run the bowl dry or almost dry.