I'm a new guy- got a 61 GMC 1/2 ton with the 305. looks like someone might have installed a later model carb since it appears to have an adapter on the manifold.2 bbl Holley -only numbers I see is 6R1919B cast on top of the air horn. looks like half a dual float Holley with a full size top about like a 4 BBL would have. so far unable to find a parts house that can find the numbers. the fuel pump diaphragm is dripping and I need to fix this thing. anyone dealt with this one? just bought this old truck and want to get it going again.. Raymond