Fuel pump cut off switch

I want to put a cut off switch in my fuel system.I want to be able to crank the motor over (to build oil pressure) with out the motor starting.I was gonna splice a switch into the gray wire coming from the fuel pump relay to the pump,but I'm thinking it would be better to splice a switch into the ground wire going to the fuel pump relay.Would this be better or not? Thanks!!

I think that version 2 would be the best/safest way to go.