I highly recommend Preferred Doors. I recently purchased a gear and pulley replacement set for my 20 year old Craftsman belt drive 1/2 HP opener. The parts were very reasonably priced and of excellent quality. What set this purchase apart from others was that it included everything needed to do the job, gears, clips, bushings, spacers, grease... They also included very thorough details on how to replace the parts, reset the limit switches test the opener and reset the wireless openers.
I received four new puleys from Preferred Doors and installed them on my old 1972 vintage garage door today. It now opens and closes very smoothly and quietly, just like new again!