1975 Charger Drivetrain Into A 1973 Duster?

The rear won't bolt in because the spring pad perch won't be in the exact right location, aside from the housing also being a different width that can be ok with off set wheels, or see your local shop that handles modifying housings and let them make it right for you.

The motor and trans i don't use motor mounts so that will bolt in if you use what we call elephant ears, that also alleviates a few other problems and depending on what you want can make for better set up of angles, centering and weight location.