Review on ⚙️ ACDelco Professional Black Idler Pulley 38018 by Matthias Foxx

The pulley bore was much larger than the Entourage idler pulley. The first picture shows the two pulleys with the idler pulley bolt in the new "replacement" pulley. Obviously the hole is much larger than 10mm. The second picture shows the position of the idler pulley near the alternator. The "replacement" pulley had a much narrower bearing recessed into the pulley. If you could find a bushing that would allow a "spare" pulley to be fitted, it would interfere with the alternator by at least three millimeters because the bearing isn't wide enough (near the edges of the pulley) - essentially the Pulley and alternator would occupy the same space.