T-Mar, I'd be very interested in seeing this direct comparison of specs between the 1984 and 1985 Shogun 2000s. As AZORCH mentioned, that 1985 Shogun frame used to be mine, and I had bought it with all the original parts intact. If I recall, the steerer on that was stamped Tange 3C, indicating a March 1983 fork build, but all those "5"s in the S/N made me believe the rest of the bike was 1985. (Also, 1985 was consistent with the date codes of many of parts on the bike).

I now have a 1984 Shogun 1500, whose serial # is more conventional (4SBxxxx) indicating a February 1984 build. Also the 1500 steerer tube is stamped Tange 4k, indicating a November 1984 fork build.

I am very curious about the differences between the 1984 1500 and the 1985 2000. My own logic tells me that there were no concurrently offered 1500/2000 models, but that the 2000 was the replacement for the 1500. Can you confirm this?

I say this because much of the equipment that came on each bike was of the same level: both had the same 1st gen XT derailleurs and XT cantis, 105-level brake levers, and 27" Araya 16A rims with Suzue sealed cartridge bearing hubs. If the 2000 was the higher trim option to the 1500, why would those components have been identical? There were a few nicer pieces on the 2000, like a Technomic stem versus an SR custom on the 1500, and a really nice Takagi crankset as opposed to the plain Sakae CX set, but mostly the comps were the same. In fact, the 1500 came with a way nicer BB: a sealed cartridge Tange with lightweight adjustable aluminum cups on both sides, as opposed to a regular loose ball/steel cup Tange BB on the 2000.

There seem to be several subtle frame differences between the 1984 1500 and 1985 2000:

2000 has three sets of bottle cage bosses, 1500 has two
2000 has fork low-rider bosses, 1500 does not
2000 has double eyelets on rear dropouts, 1500 has single eyelets
2000 has derailleur cable guide braze-ons beneath BB shell, 1500 has them above BB shell
2000 has "S" seatstay caps, 1500 has regular seatstay caps
2000 has chromed rear triangle beneath the factory paint, the 1500 does not
2000 has downtube shifter braze-ons, 1500 does not

Several features are the same between the two frames:

both have double eyelets on front fork
both frames have the same front and rear forged dropouts
both frames are Tange #2 DB seamless, with Tange chromoly fork and stays
both frames have a chain hanger braze-on
both frames have canti-bosses
lugsets are the same on both frames (except the seatstay caps)
head tube/seat tube angles are the same on both frames
rear brake hanger and cable guides are the same on both frames

With all those similarities in terms of frame material, geometry, and components, it leads me to think that the 1500 was their original top touring model, and was replaced by the 2000 sometime around 1984 or 1985, with only minor changes and upgrades to the specs. Also, if I recall, the 2000 was replaced later on in the 1980s with the Alpine GT, which actually moved a little down-spec, with cheaper Deore-level mechs and Tangealloy or Mangalloy frame.

Again, any additional insight you may have into these models would be appreciated, T-Mar.