Although not on a classic old bike, I had the opportunity to try a 5mm change in fork rake on my fillet-brazed steel Bilenky, certainly a "classic" in my book. I use a Look HSC 1 fork on that bike and the Stephen built the bike for me to require only a 9cm stem, this after I complained that I never had a bike with a long enough top tube!
After I rode it for a while, I found the handling too stable for my tastes, perhaps only because I'd gotten accustomed to ill-fitting, quick-handling bikes - we'll never know for sure. But whatever the reasons, I ordered the identical fork but with more rake to give me less trail (did I get that right?) and the bike is indeed snappier in handling, but the difference is really quite small. I like the way the bike corners better now - before it felt like I had to somehow work or force the bike to turn, almost as if it wanted to go straight no matter what. With the change in fork, the handling feels completely natural to me. I did ask for a stable handling bike, and this proves that you do indeed have to be careful because you might get what you ask for!
Again, let me stress that such a single change in a bike really does result in a very small change in the way a bicycles handles, at least according to me. I imagine that I might have been hard pressed to tell the difference between the two in a blind test, and certainly in anything but relatively hard and fast corner I can detect no difference at all.
Steve Freides Up the Road from Chris Beyer in sunny Ridgewood, NJ