I have heard, but have not yet checked, that the old style have a key on the pump shaft, where as the new style don't. I was also told with the new style, the hub is timed in the factory and should be left where it is. The reason I am looking for these parts, is I bought a backup pump, with this new style pulley, but it doesn't do me any good unless I can mount it. I thought I coould just use my old one as well. Also, the pump housing does not have the slotted mounting holes, so timing would be impossible without the new style pulley. Thanks anyway.