I built a 1994 Toyota pickup and swapped in a OM617a mechanical diesel. It's a really fun party trick to unplug the battery and have it continue running.
In terms of security, it's my most secure vehicle. Mechanical diesel means its gonna need to be glowed which I have it setup as a push button and no thief will know this. As well, my shutoff switch is a toggle switch under the dash I leave to "off". It'll just crank and crank forever. And my biggest security feature? It's a manual transmission. Most see that and won't even try.
My first car was a used 1976 MGB. Some models came with an electric overdrive, mine didn’t but it still had the switch in one of the steering wheel stalks. A friend showed me how to switch some wires around so the unused switch would control the fuel pump. That was the extent of my theft protection, with the loose rag top there was no point even locking the doors.
In terms of security, it's my most secure vehicle. Mechanical diesel means its gonna need to be glowed which I have it setup as a push button and no thief will know this. As well, my shutoff switch is a toggle switch under the dash I leave to "off". It'll just crank and crank forever. And my biggest security feature? It's a manual transmission. Most see that and won't even try.
Security by obscurity