A 30 year old original GN system would not be a good choice for anything
As far as function, fit, ease of installation and looks go, the Walker system IS the original GN system AFAIC and I would say it would be a fine choice for a very mild car that you want to keep looking stock. All parts needed are cheap as hell too.
With that said he's still open to other choices. Just would like something better than a stock single exhaust....