Just thinking about it... You'd end up with a bike that looks exactly like an SV thou. It'll probably end up less good as well, and there's practically no chance it'd be cheaper- plus of course, the resale value would be pennies.
Engine swaps to create something truly different (the 7/11 or Gixxer Zeds being classics, or a Scoobydoo WRX engine in a VW Beetle) that's one thing, but it just seems like this would be reinventing the wheel.
I'm still thinking old Lester was right... With the work involved, it'd be better to build a whole new frame. I want a Spondon-framed 636, if I had the funds I'd order one today