I had a new 79 Aspen R/T E58 police 360 back in 79, 8.25 2.72 gear SureGrip. My 8.25 axle was damaged when I slid into a curb. I bought a 73 340 4 speed Dart from a junkyard and swapped in the 8 3/4 rear end from the Dart into the Aspen. Everything swapped over as an assembly, even the pins on the perches lined up with the holes in the leaf springs! It was a DIRECT bolt in swap! Shocks, brakes, etc all lined up and swapped over to the 8 3/4 like it was made for it.