MORE great information here.
I don't know much about the 73-76 DRUM brake cars except that they used large upper ball joints....the same UCAs as the disc cars. I didn't know that the lower ball joints were standardized but it makes sense, 1973 brought several steering and chassis changes for several Mopar models. Thank you for that bit of information. It is great to learn new things.
My discoveries here pertain to the differences when changing 1972 and older drum brakes to a 1973-76 disc brake arrangement. Sometimes people pull spindles and rotors from an Aspen or Volare, even other B and E body cars built after 1972. Those all do have what has been called the wider track.
This 76 Dart was originally a disc brake car but all the stuff was gone when I bought the car. I bolted on some rebuilt drums I bought at a swap meet in 2021 because I just needed something to make the car roll onto the trailer.