Ironically, if you were to build it with period correct components i would imagine it would not only ride as it was intended when the design was thought of, it would also perhaps be far less desirable when used and left outside a shop, pub etc.
Hunt down period correct components, the frame deserves it. There's no reason why you can't ride it instead of just polishing and looking at it, is there?
Love these types of builds. Its gonna be a challenge finding period parts for this and big £££s even for decent used condition. Id build it with 83/84 parts as they are more plentiful and cheaper.