Hello,
In looking up more info on my 1989 Schwinn 974 I happened onto this thread, I know the above poster referenced an old thread with dead people, but I do have some info I can share with you regarding your 974.
I tried to attach a 1989 Schwinn spec sheet for their aluminum line. As far as Schwinn's hierarchy of the sport bikes in the '88 catalog seems to be Avion (later renamed Ontare and finally renamed the 974), Circuit, Tempo, Premis, Prelude, LeTour, Traveler, and World Sport. The Voyageur was in it's own category as a touring bike, and the Paramount and Prologue were in their own category as racing bikes sold as frame sets only. The Premis disappeared in the '89 catalog and the Paramount Design Group aluminum line is officially introduced as the 974, 754, and 564. Gary Klein was reported to have gone to the new Greenville factory to help educate the select group of welders who were going to be building Schwinn "Aluminum" race series (I can't verify this info regarding Gary). Schwinn built a new factory in Greenville, Mississippi, all the higher end American frames were being built there. It was a money pit, Schwinn couldn't compete with Asia's cheap labor and price point, and the plant closed in 1991. That officially ended "Schwinn" as we know it.
The important thing to remember about the 974 are the forged seat stay yoke, the forged rear drop outs, and the chroming details... these aspects of the 974 were expensive, labor intensive, and not "mass production" in design. The 974 was not assembled in Greenville, it was assembled by PDG in Waterford, Wisconsin. When the employees of PDG bought the facility from Schwinn and preserved the essence of the "Paramount" and "Schwinn" names by starting Waterford Cycles. The President of Waterford Cycles is Richard Schwinn, so there is a direct lineage to the famed glory days when Schwinn was America. The point I'm trying to make (with my wordiness, sorry) is your 974 is basically an aluminum Paramount race bike without the lugs of their steel frames. Your 974 is every bit as good as anything available today (that is crafted in metal). In 1989 the 974 frame and fork sold for $600.00 and complete with the Shimano 600 (Ultegra) grouppo was $1,000.00. That year a Paramount painted (not chrome) frame and fork set sold for $700.00, compare that to my Schwinn Circuit (top steel frame bike available) with the same 600 grouppo sold for $900.00. The 974 sat higher than the lugged Columbus SL Schwinn Circuit but just below a lugged Columbus Paramount. The 974 represents the best and most cutting edge in Schwinn's development and (for me) it was their last gasp effort to remind the world what Schwinn achieved over the years. These days, you could certainly get a high tech carbon bike that weighs 15 pounds, spend thousands of dollars, but you will not have a road-worthy safe bike twenty years from now like your 974. Your 974 was crafted with materials that do not have "safe age" factor, carbon ages and looses its integrity, simply put that old carbon frames are not safe. Just look up catastrophic failures involving carbon fiber bicycles... you'll be more than happy to throw a led over your 974! I hope this helps. Unless you are ready to buy a Paramount or a Klein Quantum, ride your 974, and be happy with that great trade!
My 974 was stolen but I found the tweaker that stole it and I recovered my baby. I ended up customizing it because the scumbag had messed up the paint etc.. I have some pics and a description of the build over on Velospace.org, here is a link:
http://velospace.org/node/28328
I'm proud of the build, just as I'm stoked/proud to have my 974 back! I also have a 1989 Circuit, Schwinn's top-of-the-line Coulmbus SL steel race frame that was made in Greenville... I love steel road bikes... but it's nowhere near the rocket the 974 is, not ever close! I think you pulled an awesome trade, came out way ahead on the deal, and you should ride the 974 for another twenty years!
Happy New Year!
-DON-
Thanks for the reply. My 974 could also be 1991 vintage. The STI could have been an upgrade that was added later. I have the same seatpost with the internal clamp. I was told that a seat post clamp could be used if a one inch slot was cut into the top of the seat tube. I won't try that unless the internal seat post clamp fails. I still think the frame is a Klein. If you will look at a 1991 Klein Quantum frame you will recognize your bike. I found a few on ebay that had good photos. The frame is incredibely stiff and still seems to have a lot of life left in it. It doesn't appear that Schwinn sold very many of these, since you and I seem to be the only current owners of this model. 
