91 gt question getting angry?
Well, inspection cover is not a very popular item, so you may find it hard to find. The dealer has these at their parts department on their system, so you may take a peek at their screen to see What they look like.
Also, Mustang II is not very popular either and gas filler neck seal is not something you pick up at your local Kragen store.
You're looking for odd-ball, rarely-will-you-ever-need parts,so you won't find them except at junk yards or the dealers for these items.