What is interchangeable on my 64 Dart

Yes, just use later parts. To do the fronts, it depends somewhat on what brakes you have now, and what brakes you want to end up with. If you have 10" drums and want to keep them, hubs and drums will get you there. If you currently have 9" drums, you'll need to replace pretty much everything with later parts (upper control arm, spindle, brakes and lower ball joints). Read the Mopar Action disk swap article http://www.moparaction.com/Tech/archive/disc-main.html and search the archives here.

In the (7 1/4") rear, if you have 10" drums, you can swap the shafts and drums with later parts. If you have 9" drums you replace the entire axle assembly.