If its' worn,you will see it,no measuring needed.They usually get a step worn into them where the bushing rides.If its' smooth and straight,its' OK.I don't know the measurements,all the ones I have are worn bad.You can measure the area where the bushing doesn't ride,I'm assuming that the factory bushing-clearance is only a few thousandths at best(I would guess .002"-.004").Much more than that and its' gonna wobble.
