OK, but if you install such a pulley, it will change the ratio between the spindle and the feed pulley. When Monarch did the same, they increased the diameter of the feed pulley so that the feeds would not change.
Monarch also modified the spindle. They added threads at the end for a castellated nut and lock washer with tabs so that the pulley can be tightened against the motor pulley & spacer. There is no setscrew in that pulley.