What changed in 73?

You pretty much got the exterior covered, but depending on what year you are going for, the fender and quarter side marker lenses were changed from 70-71. 1972 and up went to the corporate standard side marker lenses.
The interior door panels were quite a bit different. The 70-72 cars had the metal upper and lower door panels and quarter window surround. The 73 cars and up used plastic. The other big change was the space saver rear fold down seat was added as an option in 73.
Thanks, I got all that covered. Concerned about drive train, suspension, steering etcetera
Column will work.
Rad support . Tail light supports, leaf springs and front hangers, Doors and inner quarters, Seat belt location on 71 , Fender splash shields, Just some things that were not mentioned but could effect a parts list.