That's one reason I went with a gear motor at 105 rpm's. Another plus is the fact that now I don't have as much stress and wear on the mill bearings that I would from a belted application and less danger from moving parts like belts and pulleys.
How do you BBQ an elephant....first you get your elephant....
I would make it the same width but it really doesn't matter. I would also use a lathe or drill press to insure that you are drilling exactly down the center of the bar stock or you will get a wobble in the pulley.