Our Opti-spark distributor had been replaced about 30,000 miles ago and was working fine, so we reused it. These aren't known as real long-life parts (ours could be considered borderline), so it's probably a good idea to replace. Note the splined water pump drive shaft just above the Opti. To prevent future leakage, it's important to insert the shaft with the lip of the new seal flapped to the inside--a seemingly impossible task. You don't want coolant dumping right into that distributor!