Classic Auto Air Belt alignment fix

have been looking around, I see that there are 4 grove big block lower crank pulley's out there , a lot on E-Bay, some are stepped, 2 groves are a smaller dia. then the other 2 groves. also Mancini has a new Billet Aluminum 4 grove for 108.00 cvf scrl 4cr hf is their part number. The 4 grove big block pulley used on this web page was it a stepped one or are they all the same dia. ?