I thought about this for a little while. I had 7 speed Shimano 600/105/Dura Ace STI group on my Merckx and wanted to do an upgrade to 9/10 speed. I just wanted to replace the brifters, rear derailleur, chain, and the wheels, but ended up finding a slightly used 9 speed Ultegra group that had everything but the chain, cassette, and the wheelset. 8 speed stuff can be hard to find, but it is easy to find 9 speed stuff with roadies wanting the latest and greatest and upgrading to 10 speed. You should be able to find some 9 speed 105 or better Shimano parts at reasonable prices. It is finished and its maiden voyage should be later today (pics coming too I promise).