Just to clarify, the early Auburn units were OEM. Chrysler used both disc and cone units as original equipment. The Auburn [ cone clutch ]was used starting in either very late '60s or early '70s. In so far as I know these were only used in 489 case units. Earlier 741 & 742 cases used the disc type clutches. Either one can be used in either case so long as you use the correct side bearings. Later Auburn units are an aftermarket design. If I were going to buy an aftermarket limited slip, I think I would go with a Torsen type diff. at least for street or autocross use. No doubt the aluminum case is the strongest of the 8 3/4 rears, but if you have a LOT of torque and grip the Dana 60 is still the gold standard.