Balancers go bad. This is a common problem. You need to get a new one. I wouldn't even start the car if you know the balancer is spinning on the pressed rubber.
You may want to do a search on the PY site. I thought you could still get a factory GM one and I think the Pioneer balancer comes highly rated as well but I'm not %100 sure.
Please be more specific. Do you meaan on SEVERAL balancers? Or just one or two "used" ones? What is the car used for? Is it a racer or street?
Pioneer DA-4551 is the stock replacement unit and is very good. About $100. Pioneer also offers "street performance" and SFI-approved balancers, of course for more money.
