I can't comment on a lot the frame fitting details, as my info is taken from old magazines and there are no pics, only specs. So what I have are bits and pieces and not a complete product line.
In 1983 there was a 2001 Touring model. I assume the model number came from the tubeset, as it is Mangalloy. Derailleurs and cranksets were Deore, while the brakes were 600EX.
In 1984 there was both a 1500 and a 2000. Both have Shimao XT derailleurs and cantilevers. The 1500 is listed with a SR CRC crankset, while the 2000 specs a Takagi XT. However, the big difference is in the frames, with the 1500 not having CrMo stays and forks. Both are listed with 2 sets of bottle bosses.
For 1985, it appears the 1500 was replaced by a 2500. Tange 900 main tubes and Mangaloy fork. SunTour MounTech derailleurs. Dia-Compe cantilevers, Sugino TGT, 2 bottles.
1985 model 2000, CrMo DB (no brand mentioned), Deore XT derailleurs and cantilvers, Takagi ART crankset, 3 bottles.
I don't have data for 1986 but the 1987 Alpine GT appears to have been a replacement for the 2500. Tange Infinity, Shimano Deore derailleurs and cantilevers, Sugino VP, 2 bottles.
So it looks like the 2001 Touring became the 1500, which became the 2500 which became the Alpine GT. They appear to have been Shogun's entry level grand tourer. While I only have model 2000 data for 1984 and 1985, it's obviously the upper end grand tourer. It probably existed in other years, though possibly not under the same model number/name.
It's really strange that the fork and frame on the 1500 are separated by 9 months. A November fork date would typically imply a 1985 model, but the 1985 version would appear to be a model 2500. I wonder if the fork might be a replacement, either due to a warranty issue or a crash? Given that your fork is CrMo and both the 1984 1500 fork and the 1985 2500 fork are listed as non-CrMo, it would seem to be a possibility.