My favorites are the pre-cantilever chainstay '87-88 SR500's and SR800's, the ones with full Shimano 105 or Tricolor 600. Six (or seven) perfectly indexed rear gears, everything can be rebuilt & totally bulletproof. Came with Biopace rings but they're easily swapped out for any Shimano round ring (although many people like 'em). Simple to upgrade and will take a 130mm rear wheel without a problem. Not such a fan of the Suntour setups used during the earlier periods, but others like 'em.

Look out for: Crappy paint (can be touched up, tho). Shredded brake hoods (hard to find replacements, easier to buy a replacement lever set). Expect to replace all cables, housing and tires and most likely the saddle as well. Anodized rims will generally have lots of (unsightly) rim rub but will work fine, but check corrosion at the spoke eyelets- a sure sign that the bike was kept outside or in the damp. Top tube cable guides are a particular sore point, as Cannondale no longer has a supplier and no intention of sourcing new ones. Old ones are brittle and break off easily. Jagwire makes a stick-on one for hydraulic cables that works but is not quite as elegant.

Don't know what size you are looking for, but give me a shout if you need a 58. I think I have a few still in storage in boxes.