I talked with a Pertronix tech rep today. The Pertronix part number 2561 is the conversion kit for the IAT 4416 10T distributor. I purchased one from CBS Performance in Colorado for $109.00 (company recommended by Pertronix: they have the units in stock). They pay shipping. The man with whom I spoke has installed this unit in our distributors and said there were no problems. When I receive the unit and get it installed, I will report back.