I know I am quite late getting in on this thread, but I'm surprised that no one has suggested the best of both worlds... Cut off BOTH the Injectors AND the Ignition. It would be a less than complicated bit of wiring to have a couple relays work off one momentary switch. Just an observation, as I plan to make the above mod to the Rolling Lemon in the very near future.
Also, a question for all those that are far more informed than myself, If the injectors are shut off and the fuel pump is still running, won't that cause undue stress on the fuel pump? Or is there a return line on most fuel injection systems that prevents this? All comments are appreciated.