Parting out a 66Dart GT

Hello
I'm intrested in the rear end complete. I'm needing one for a 1974 duster.The center to center on the spring perches needes to be 51.400 inches, I don't know what size the earlier modles used. do you know the measurements of the rearend?
How much for the complete rear end including the brakes and shipping. what bolt pattern are the lug bolts?

Thank You
L. Samuels