I had a guy turn the pulley to fit both the spindle and motor shaft. I use a Gates 5m belt, a rather small V belt. It's always worked really well for me. If I had to do it again, which I plan to do myself this time, I will use the same V belt but will use two of them on each pulley. A single belt has been very reliable and can stand up to way more load than I would have expected, but i does show some wear. Also, it would provide redundancy, so if one belt would fail I know I can keep working with one.