There is a thread started over at Moparts that I'm sure when snowball, but from what I gather, the RS is an evolution of the Borg Warner (and later, Tremec) T-45. I could be completely wrong on this though.
By the looks of the specs, the torque capacity is pretty modest and won't match that of the TKO's. They look to be pretty well suited to small block, and mild big block applications.