What should I buy? Frame wheels cranks bars tyres mudguards grips pedals spokes bike

I'd go for modern parts. On the whole they are better.

If it's not every day* I'd say go for the full campag (*not *campy), then use a deda finishing kit. Silver drive train/hubs spokes, and then black carbon for the seatpost, stem, bars.

• not because of campag parts in general, but just because you'd want matching hubs and they're not sealed (I think?).