The 85 GT is going to have the notched molding and any fastback is going to have the smooth. The molding is actually a part of the rear fascia there is no way to change it. The front can be modified to make it appear smooth by adding the turn signals with the smooth molding and changing one little piece. I would suggest picking up a smooth molding rear fascia to make it look right.
As for the rest of the parts, you need to get lucky and find someone near by parting out a fastback and buy everything you need at once. It gets expensive and time comsuming to piece everthing together. Sometimes you can find someone willing to ship the whole kit but that gets expensive. Nevertheless that's how I did it,so it can be done. I would just ask around, maybe Songman will ship his stuff to you? Since I have done my own swap I may be of some assistance to you. Good luck.
- Jonathan
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1988 GT (Firebird Interior),1988 Coupe (Daily Driver), 1985 SE (Project Car), 1985 Coupe (parts car), Firebird Interior Installation Website