You want to measure full manifold vacuum at idle, warm, in gear if an automatic. This would be from a source below the throttle blades. Power valve should typically open a 1/2 idle vacuum, ie if you have 12 inches of vacuum at idle, a power valve rated for 6 inches of vacuum is what you want. Not sure about your carb kit, but if you carefully compare the gaskets, it may work. Can't answer question about carb removal.