I'm doing a motor swap on an older Bunton 52" w.b. It was way under-powered with a B&S 12.5. I have a Kawasaki FC-540 for the swap. The variable speed pulley is now too small a diameter to fit on the 540 shaft. Do they make different size pullies to mate to different size shafts? Is there such a thing? Or should I just get a couple of solid pullies, one for the trans. belt and one for the blade belt and let her fly.