If he is running an electric pump the oil pressure switch will at least turn off the pump if oil pressure drops. If you get in a wreck or something the pump will still pump fuel if you don't have a pressure switch.
I realize why it's being done, but an inertia switch would be better for that I think.
That way you don't have to also install a manually operated bypass switch so the engine starts in the first place. (especially if the fuel has evaporated from a carb)
If a gauge for oil pressure isn't enough comfort put a buzzer on an idiot light switch.
Obviously the OP is going to do what he wants, but I thought I would offer an alternative over all the wiring and possible fail points being added into the system.
