All, in the picture on the right you see what comes in a 70-74 small block heater hose nipple kit. It is 1/2 inch to 1/2 inch. However, the one on the left is the original one to the engine, which is a 73 340 by the way. It is 1/2 inch to 5/8 inch. It is from the original manifold that came on...