verifying fit 72 donor to 74 car

I used a '74 fender on my '72. The only difference I could tell between them was a bracket attached to the front that holds the grill attachment piece on the '72. I welded on a homemade bracket to the '74. So, imho, you will just have to cut this bracket off for it to fit your '74.
As to the interior, the sail panels have a very different shape, the '72 is a lot shorter and uses a cardboard sailpanel piece in addition to the metal item. There might be some difference around the quarter window, but I am not sure. I have always wondered why the earlier metal panel couldn't be used.
I can't help you with the headliner item, I don't recall.
C