If the balancer were not really needed-- do you think the manufacturers would have spent the money to install them? They are there to do just one thing--- dampnen the harmonics in the crank-- has nothing to do with the internal balance of the engine. if you look at some of them, they have a rubber insert to allow the outer dampner ring to float. As for the driven speeds of the accessories, that is dependent on the pulley size-- which bolts to the balancer so you can install whatever size you need on the balancer. On some of the old engines, it was in fact just a cast plate to bolt pulleys to, or it was the pulley itself.
