Well, the question is do you want to make this a period piece or a rider? If you want to make it a period piece, you'd have to find some Robergel or Stella or possibly Union spokes to respoke the wheel with and you would have to keep it original, which would mean keeping the 27". Of course finding those spokes could be a hunt for a needle in a haystack.
Otherwise, if you are not going to be concerned with the scrutiny of the purists at the next Classic Rendezvous get together, put 700c wheels on it and ride!