I'd definitely say it's a '78 AMX. Even if it is a '77 AMX, it is still a VERY RARE car either way. If there is anything else left on the car (which is special to it), you should remove them! They are hard to find!
The Targa band looks like it is still on there in one piece, I would remove that. I've heard it is a PITA to remove, but done correctly, you would have a very rare part.
Also check the spoilers/flares. Those were special to the '77/'78 AMX's. Look around for anything else maybe inside the car, since the grille is missing in the picture, look inside the car, maybe it's in there. The '78 AMX had a special mesh grille with the special turn signal lamps inside the grille. Also a VERY RARE part, that would be sought after if a person were restoring one.
Bottom line, get everything you can off that car. Even the bumpers, they were prone to rusting out in those years. If they're good, take them! They're pretty rare as well...
Too bad the owner who owned that car didn't know how rare it was... makes me sad to see it sitting there in pieces