I have mating parts, just wondering if one is better than the other. I assume the late model 3 ring must have been enough of an improvement for the factory guys to switch. But it doesn't seem to be a big deal for the aftermarket. Looks like the most popular aftermarket input shaft is the two ring style although A&A does sell a super duty input shaft that is for the three ring config. Maybe it is a better design but most people don't have the matching parts?