Didn't do to much fabrication. When we installed the 72 tail panel there was a space in the trunk we had to make some patch panels for because of the difference of how the bumper mounted.
Also had to remove the front bumper supports from the frame of the 72 and install them in the frame of the 74 because of the different way the bumpers mounted.
Made a couple patches to repair the lips on the front fenders also.
Biggest mod was replacing the 74 tail panel with the 72's. Lots of spot weld drilling and welding.
One other thing I can think of was repairing the spare tire well.