Genuine XA & XB GTs are getting up in price. I kick myself when I see it. I nearly bought a clean XB GT about 12 years back for $7K and now they are going for at least twice that.
Check out some of the Aussie car trader sites and you will find a few.
Carpoint
Here is a search I did, I hope it comes out.
Carpoint Falcon search
Craig (750HP) is a bit of a Falcon nut with a 460 powered monster. He migh know of some good ones for sale.
Cheers