Good luck finding a Columbus SLX frameset in good condition for reasonable prices, as they are presently the "holy grail" of frame material for classic steel bikes. It's that internal "rifling" that seems to really soften the knees on collectors. You'll have better luck finding an SL or maybe even Reynolds 753 frames these days at close to affordable prices.
Just a heads up as you dive into the classic steel racing frameset market.
You can always set your sites a little "lower" and just find a good ole 531 frameset instead as there are lots of the true and tried framesets being sold out there everyday, plus 531s always seem to garner great respect as it has had a long and legendary history in racing bikes....and even land speed record vehicles!

Uhmmm..alleycat racing??? What the heck is that all about??!!

Chombi