Happily even with almost 70 years of use my Uni passes the dime test with solid belts and the original pulleys. That's the beauty of the Uni - all that mass and a solid design soak up potential vibration that would make a modern contractors saw dance.
When I rebuilt it, I considered swapping the arbor pulley, but it's matched to its old school 1725 RPM motor pulley, and not buying it saves me money that can go into other machines (like my "new" 1952 HD shaper).
Pete