I find the original '87 Black Lightening to be the nicest version. Spring was a very high end group and the bike looked really good. Later versions weren't as high end in their components.

Here's all the old catalogs for your viewing pleasure.
Cannondale Catalogs | VintageCannondale.com

I had an '89 3.0 frameset and my dad has an LL Bean Cannondale sport touring bike from the early '90s. Sidepull brakes, friction shifters and metallic paint. One of my friends at the time had an '88 SR600 with the blue Pegoretti paint job, and another friend had the Crest Team bike.