Niles, set the pressure with the motor running (but it shouldn't make much difference).
Another safety suggestion, you might want to consider wiring an
oil pressure warning light switch into the switched power circuit on the fuel pump, with a manual override. That way, you can get in the car, prime the carburetor with the override and start right up, but if the motor ever quits (accident, etc.), the fuel pump won't keep pumping fuel, possibly through a torn fuel line.