My idler pulley grenaded on my way into work last night. I got a gates replacement pulley from O'Reilly, but the dust cover for the front of the pulley will not fit in the inside diameter of the new pulley. The pulley did come with a new "spacer" but I'm not sure if it should go on the front or the back of the pulley as I've seen videos of replacement pulleys with a rear dust cover instead of the front. The xj is a 94 with the 4.0. Any ideas?