I took my Dad's old racing bike from the 70ties and most parts from my race bike with which I had a crash and the frame broke.
So, what we have is a vintage steel frame with rare swiss BB, the original fork, stem, handle bar, crank set, down tube shifters and very comfy leather saddle and the 'new' parts such as Dura Ace 7800 rear derailleur, Ultegra 6600 front derailleur and Mavic Ksyrium Elite wheelset.
First I thought it's a one day work, but fitting the new parts to the old frame took a lot of research and searching for adapters. But now it works and rides very very well.
And, this year will be the 100th TdF thatswhy the yellow bar tape, cables and the in-the-dark-glowing pedals!