I have wanted a Klein since the first time I saw one. But as you can see mine is pre Quantum Pro. Still the frame was an industry inspiration and in my opinion moved us a bit forward. They had beautiful welds, unlike many aluminum bikes today they took the time to smooth them out so it is hard to tell it was even welded. But Shimano had already come out with the Dura Ace 7400 STI shifter in 1990. In 94 they offered the Quantum Pro and it had Ultegra shifters with internal cable routing. As you can see mine still had the eyelets on the top tube. Some of the Cannondale race bikes came with the 7400STI and by 94 there were a lot of conversions for the derailleur guides. Remember they even had the Stem shifters on some bikes back then as well as bar end shifters.

You can still find 7400 STI shifters on Ebay and I am sure the ultegra shifters are available as well. But if I did it again I might not stick to vintage shifters. The Klein comes with 130mm rear dropouts so mounting a modern wheel is no problem so it will take a 8-9-10 speed cassette if that is what you want.

Gary Klein designed the Quantum with a very stiff rear triangle with big chainstays. When you jump on the prdals for a sprint there is no side flex even if you are a clydesdale. That being said I find using a higher spoke count wheelset and 25mm tires tame the beast for everyday riding. About once a week I bring it to our group rides and I have no problem staying with the group for 40 or 50 miles. It is quieter than my CF bike. As you can tell I am happy with my score on this bike.