The reinforcement washer on my 66 SS was installed on the inside of the water pump pulley. I understand the 66 washer has part number 3720616 and is 3 1/4" OD and cup shaped and the 67 washer has the same part number; but is 3 3/16" OD and cup shaped. I believe I have the 67 washer because it fits inside the pulley(I have a 66 pulley and water pump); but not flush if put on the outside and the diameter appears to be closer to the 3 3/16" width of washer is about 1/16".

GM Restoration parts has the 3720616 was available. But my CD part catalog indicates that the 3720616 is for all 62-68 cars. So does anyone know if I order the part from GM Restorations if it will fit inside or outside the water pump pulley

Since the washer will either mover the pulley in or out 1/16" will this have any effect on the position of the alternator pulley?