I can't figure how to remove the inside upper door trim, on a 1968 Barracuda Hard Top Coup.

You would pull the rear seat to pull the package shelf anyway and I'm almost certain the side panels have to come out too. The upper rail trim might be last out and first in. Although I've done this a couple times, its been a while.
Those clips in the floor that hold the seat bottom, I covered them with hubcaps, then blankets. They would eat you knees.