Don't be intimidated by tales of wildly overpriced vintage stuff you'll have to score from ebay and blah blah whatever. Vintage bicycles are very wallet-friendly unless you are going for a full restoration on a truly special bike. Get the one that fits you better. Expect some outlays for tires, cables, etc., but I've found most old components clean up to solid functionality unless the previous owner has truly beat them to hell.
And as suggested above, spend some time in the Classic & Vintage forum.
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A race bike in any era is a highly personal choice that at its "best" balances the requirements of fit, weight, handling, durability and cost tempered by the willingness to toss it and oneself down the pavement at considerable speed. ~Bandera