Inner fenders are 71-2 only 73-4 has completely different inner fenders even from small block to big block on the passenger side.
Trunk floor is the same 71-3, 74 is it's own raised trunk floor.
Front frame rails are 71-2 only as the 73-4 front rails are different and has a completely different suspension where the upper control arms mount to the k-member not the frame rails. The front floors and rear floors can be used. I believe the rear rails are the same.
Keeping in mind while some of these parts will fit there are some differences in appearances and body plug sizes in the panels but they fit.