I had my electric fuel pump wired through an
oil pressure switch plus the Battery Cut off switch would stop all battery power. If the car is upside down any left over fuel in the Carb would go into the air cleaner if it leaked out and not into the cylinders. I also had an extra toggle switch wired to just the fuel pump which would cut it off alone. But this was so I could work on the car with the ignition on and the pump not running.
I think that in most cases everything would shut down quickly and if there was any fire it would come from the leaking fuel hitting a hot exhaust of something like that.
Ron