"Though long in coming, the Powerflite (introduced in 1954) is an obvious example of the famed Chrysler engineering. The engineers had done their homework well in creating this two-speed planetary "gearbox" with a torque converter."
http://www.allpar.com/mopar/powerfli...ktrack=kcplink
So this obscure 57 year old trans. is the basis for the 2011 drag pack trans.