Hmm. Trying again.

my friend has a system on his 72 where you can easily get in the truck and drive about a block and the truck will shut off the carb and everything else in the truck and then you cant get it budge at all, what happens is when the truck ignition switch is bypassed it slowly shuts everything in the truck off and then you are out cold

Old Rusty C10, that one got me laughing. :D

I put a electric fuel shut off from a truck that had a propane set up
and a ford type solinoid on the main battery cable, with a small bypass wire to run the memory and switches but will burn out if you try to start it with the solinoid not energized

On my EFI car, I simply unplug the power to the computer (OBD1, so no problems) on the truck... there was two ignitions, a tractor style under the hood, hidden under the washer bottle and the one in the cab. in high theft areas there was a pretty strong cable or chain running between the two rear wheels, through the spokes(white wagon wheel type). That and a sticker that said: "owner is not afraid to kill to protect personal property" That and I usually ALWAYS parked next to a BMW, Lex, Acura, etc. Newest "car to be parked next to" is the H2 and any GM SUV.

On a CRX a friend has, there is 4 switches, one to start, one for main power, one for fuel and the ignition. you have to hold the ign. over to start, flip the main power switch then hit the starter button, release the key and filp off the master power switch. confusing as hell if you are trying to start it and you dont know the right way to do it.

The best deterent is not to have anything that anybody else would want, or at least not have it visible. If you do not want your stereo stolen then do not have it visible in the dash. Most criminals rely on easy targets.You like having nice tunes? Get a cd player that goes under or behind the seat. I have a 10 disc that also acts as a radio tuner the only part that is visable is the remote for it. When I park the truck I will hide the remote as well. I also have a quick release for the steering wheel also. It is pretty damn hard to steal when you can not steer it. But if they are determined enough, have the opportunity and have the time they will get it. I just have to make it as hard as possible for them to do it. Just do not make it easy for them.
The best deterent is not to have anything that anybody else would want, or at least not have it visible :D

An old girlfriends dad had a set up that locked you in if you didn't push both kill switches first. He had a loud alarm and stobes under the car that went off while you were stuck in there. The best part...

The alarm speaker was in the car!!!
Stuck in a car with a 120Db horn beneath your seat is no fun.:D