I think there was lots of Titanium xizang frames hanging around in one of the GT warehouses after the Zaskars came out so they was changed to v-brakes from cantilevers for late 96- 97 and called it the Lighting
Assuming that statement was not intended as a joke, it is wrong on so many levels.
The Lightning was an Asian made frame that was sold as a complete bike equipped with an STX/LX mix. The material may be the same, but the craftsmanship is not, the crude stamping on the endcap and the weld quality are two obvious differences, along with the blasted finish instead of the very expensive hand polish on the Xizang.
Xizangs from this period (97-99) were made in the GT Tech Shop in California, and to the best of my knowledge are identical to the frames used by the factory team. The frames were compatible with both V-brake and cantilever for 1997 and 1998 (the small loop on the back of the seat tube on these years is for mounting a stop for cantilevers), they were V-brake only for 1999, the last year of production.
There's nothing wrong with the Lightning, it weighs about the same, size for size, as the Xizang, I honestly don't know if the tubes were from the same source, but the dropouts are identical. they just don't have the cachet of being the 'team' bike. They should also not be considered the second place in GTs hardtail lineup. I personally would rank the top 3 as:
1.Xizang
2.Psyclone
3.Zaskar
Depending on your taste in frame materials you might want to swap 2 and 3, but for me a fillet-brazed steel frame trumps TIGed aluminum.