Im building a GS450 cafe and the from what I can tell almost everything is interchangeable. If you have the time / desire I would highly recommend doing a complete rebuild on just one. It looks like you have enough parts to complete 1 bike easily. But IMO it would be hard to rebuild / restore a bike just to make a few extra bucks. If it were me, I'd rebuild one. The bike is super easy to work on. If your just looking for $$$ just part out the tank, fenders, seat, and other misc parts. That's just my $0.02 but its cool to see more GS's out there. Good Luck!
1981 Suzuki GS450L Cafe Racer - Build Thread