I finally got some of those D-plates installed on my 88 Formula converted to a fastback. The seal I bought from the Fiero Store a couple of years ago had never been installed, I pushed it on all the way around. I appears to be on all the way. I set me deck lid on there and it would not close. I lifted the deck lid up slightly and could plainly see that the groove in the deck lid sides, presumably for the seal, does not line up. So it is stopping the lid from coming down all the way.
All fastback GT decklids are the same (remember, in 1985 the GT was a notchback).
Did you actually secure the decklid to the hinges and then try to close it? The ridge around the trunk area sit point on the underside of the fastback decklid does indeed hold the trunk seal in place. The way I typically install the decklid is to attach it to the decklid hinges, near close it, and then loosen up the 4 13mm bolts and shift it around until it lines up "flush" in the rear. You can try simply removing the seal and seeing if it'll close that way. then after you've made your adjustments to it's position re-install the seal and see if everything closes correctly.
