There are a few varieties on the Balancer for the z car. The most common is the two pully two piece steel where the larger alt/fan are mounted on to the hub on rubber and the smaller accessory pulley is part of the hub. you can bolt additional pulleys onto the front of this unit. The better early 240z version mounts the alt/fan and accessory both same size as one unit and coupled to the hub via you guest it, rubber. It too can bolt on additional pulleys on the front of the hub. If you continually spin the pulley on the hub, look at aftermarket one piece CNC machined units. The cost goes up but the time spent changing the unit can be a real pain. Most parts available from junkyards are not going to be long for this life, I used to change them one or two a year.