The vintage weight weenie certainly starts at the frame. Even a heavier R531 frame will feel twitchey and unsafe if you go the anemic route.
I'm always let down by cranks (820g for a triple) and pedals (498g for look clips)
Unfortunately there are big gains by going cassette, but lightweight freewheels can keep you on ultralight wheels (<1200g).
You can save 150g by using cut bars without drops. Downtube shifters are commonly around 100g and save cable length compared to brifters, even with all this though to go superlight you should start with a <2kg frameset. (Or just build a vintage track bike)