Catalog says that the 4-step motor pulley is 5/8" ID. Since those are decidedly un-common and all of the rest of what should have come from the factory is still there, I think that it is safe to assume that. Of course it would be a trivial exercise to just measure it.
Also, if the ads give the Frame Type or Number, the three that are probably the most common on single phase AC motors these days are 48, 56 and 56C. The 48 has a 1/2" dia motor shaft or shafts. The 56 and 56C have a 5/8" dia. shaft. The 48 and the 56 have a side mounting plate. The 56C mounts with 4 bolts screwed into the shaft end concentric with the shaft. Some 56C's will mount both ways. There are a lot of other variables, such as how the wires connect, but most of these variables are visible in photos of the motor.