Jon (Carb King) has been trying to give away a huge supply of "rebuildable core" Rochester carburetors for years, after giving up on trying to make them work right. So far, no takers! Unless the little triangular brass tag is still on your carb, there's virtually no way to identify what you have or order the right parts for it. There are no usable numbers on the castings. Use the Rochester for a stinky paper weight and buy a Carter carb from Jon that's calibrated for your engine.
Jerry