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texaspandj, I'd be tempted to just ride that Trek 5900 for awhile as-is. I keep eyeballing them on CL where the Trek OCLV models from that era seem to pop up every couple of months for reasonable prices.
I suspect internet scuttlebutt keeps the prices fairly low -- just enough to make it worth buying an entire bike just to cannibalize the parts. Every time there's a discussion of the early 2000s OCLV models, invariably it drifts into claims that the frames felt mushy and might asplode, because somebody once heard something from somebody somewhere.
But if I ever drift away from steel, it'll probably be titanium rather than carbon fiber. Once in awhile I see a Litespeed or Lynskey and think "I would totally cheat on my steel bikes with you, behbee."
Might be fun to build a rat rod out of the Trek 5900 frame. Something with flipped albatross or North Roads bars, radial laced wheels, blue tires, maybe a banana seat if it has rear eyelets like the mythical Centurion Turbo Allemagne TTT (time trial touring) funny bike.