Anyone know where I can find a primary throttle shaft return spring? It is the maybe 1"x1" spring on the throttle linkage that connects the front and back carbs on the passenger side. So there is a primary spring on the back carb and a secondary spring on the front carb. My primary fatigued out and won't return the throttle to the idle position. The car just races and the throttle won't return. These are different than the drivers side throttle return spring that connects to the gas pedal more directly. I called NPD, Branda, Carl's Ford Parts, Summitt Racing and NAPA and no one has them.