As others have mentioned, those canti bosses don't look original. That coupled with what looks like a very slightly uneven surface where the a set of U-brake bosses would've been suggests a modification at some point.
I had a very similar mod done to a 1992 Bravado frame back in 1993.
Anyway, the frame details such as the internal top tube cable routing, the double eyelets on the dropouts, the integrated seat-clamp and the curved seat post hole, point to a lower end GT from 1991 or 1992.
Higher end 92 bikes would've had the 'groove tube' and no rack mounts etc.
As far as I know, none of the 93 bikes would've had any internal cable routing, and wouldn't have had a U-brake.
So based on the frame details, I reckon it's an either a 91 Timberline or a 92 Timberline or Outpost.
The frame weight also ties in with this too.
As far as a respray is concerned, a frame modification would have also most likely meant a respray at the same time. If the frame was properly stripped then there would be no evidence of overspray from the original colour anywhere inside the tubes.
Have a look at the GT catalogues in the archive for some comparisons: --> http://www.retrobike.co.uk/gallery2/mai ... emId=10499