Connect one of the black wires to one side of the pressure switch, the one without the capacitor. Wire the power feed (+) to the wire with the capacitor, to the other black one to the other wire (-).
This will wire the pressure switch in series to the pump motor.
In the 70's the hook up hose to the tanks was a black plastic hose like is pictured. It should have safe for drinking water printed on it.
The Capacitor is there to help filter out noise made by the motor
WBCCI #5501 AIR # 49
1978 Argosy 28 foot Motorhome
Wise men talk because they have something to say; fools, because they have to say something. -- Plato