I questioned the condition of the fan clutch on a '82sd, it seemed to have excess play just like described here. Turned out to be the water pump. No extra noise or leaks, or cooling problems, just the bearing in the water pump was worn. Take a closer look and see if the shaft coming out of the pump is really where the play is originating from. It is not very obvious because most of the excess movement will be at the fan-the shaft is 2" or so and the fan is like 12", so the fan will have 6 times the movement as the shaft, so the fan is where it is first noticed. If it turns out to be the fan clutch, I'd shop around for a used one, mabee post a want it now on ebay offering to pay $10.