A friend of mine has an old (25 years?) Raleigh "10-speed racer" type of bike that he hasn't ridden for a long time and is thinking about getting out again. He mentioned to me that he'd like to replace the downtube shifters with bar-mounted shifters/brifters like he sees on newer bikes. I told him that it was not really feasible for a number of reasons since he'd probably have to change over his whole drivetrain, and his frame was built with narrower dropouts and a wheel size that's obsolete now.
Am I correct in my assumption? Frankly, I think he'll have enough trouble just getting replacement tires & tubes, let alone trying to find different shifters that would work.