I see no reason to modify my Raleigh Professional. Were I to make a change, I'd want to get a set of clincher rims to swap out with the tubulars, but I'd keep it running a six speed freewheel, simply so I wouldn't be so anal retentive about where I ride it.

The Peugeot, I'd modify the heck out of. Drill out the BB and put in a modern cotterless BB with a triple chainring, 7-8 speed rearend, bar end shifters, 700c wheels, and modern wide-honkin' sidepull brakes. Not to mention the Nitto stem and handlebars that it would get, along with newer, Aero brake levers. But then again, I want to turn that bike into a tourer or randonneur eventually, so it would all work. Even then,the bike would get all polished aluminum bits - nothing black on it, no deep V rims, etc.