Well the "A" is for Lynch Road assembly plant for a start. And I thought only the 440 and Hemi got a Dana and a 383 4-speed would have had an 8-3/4 rear even with an "axle package" like a 4.10 unless that changed in '70 versus '69?? Would anything but a Hemi or convertible have "torque boxes" ? maybe take a look? Just throwing things out there.

Mike