I just did this (well, summer 1998, seems like yesterday). It is something that you cannot do with only aftermarket parts. Most of the small parts you can get, but the seat bottom, seat back, hinges, rear seat support (seat back mounts to the support), and some of the trim items can only be had from a fold-down car. The 68-9 seats are interchangable from what I understand. If you do find someone willing to part with all of it, try to get a look at how everything is installed and take tons of measurements and pictures. Also note the installation quality of the side panels. I fought for days trying to make them fit correctly only to find out that GM just slaps them on. Putting all of it together is prety easy once you have the parts.