Personally, I wouldn't upgrade. You've got a nice bike as it is. If you're happy with it, I would replace the worn out parts with ones of the same vintage and quality. If you start upgrading the drivetrain with modern components you'll easily spend more than the bike is worth. You can still find New vintage parts over the internet, on ebay, or even at some bike shops. Anyway that's what I would do. By the way, do you know what tubing the frame is made of? Is it Columbus tubing.
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