Some significant differences between the 71/72 and 73/74 Chargers. Some parts interchange but less than you think.

- windshield/back/door glass should interchange
- trunk lid will bolt on but will need some modification of the lock opening
- fenders can kind of bolt on but will need modification to work - not all bolts will line up, wheel radius different, etc
- quarter panels are totally different - dont waste your time
- interior dash parts/gauges will interchange
- interior seats (buckets) will interchange
- interior console (slapstick) will interchange
- suspension/kframe/disc brakes will NOT interchange
- gas tank should interchange
- engine (minus mounts) will interchange

That's all I can think of right now. If you want to use specific parts from the parts car, list them and people here will chime in.