[Nickj]

I'd be going along with Vince, the trellis frames are all very good giving all the 'classic' monsters really good handling. It's actually quite flexible, what Honda et all originally lacked in their race frames, Honda had to buy a Ducati which was a big help in getting the RC51's up to the dominating form that gave Colin Edwards lots of wins.
Essentially a bog trellis frame is pretty much as good as you'll need, what lets the down is the suspension so before anything else expensive get that sorted.
Real life example, my S2R feels fine until I ride it back to back with my 748R then I notice that it isn't giving me a fraction of it's potential. A good Nitron, Showa or Ohlins and Showa or Ohlins front end are on my to-do list.

Nextest make sure you have the 900, not the 750 heads fitted.

Then lighten as much as possible, Ti valves & conrods would be good, drop the flywheel mass.
As Utopia has said less mass to spin up means faster spin up so lighter wheels are a bit of a no-brainer.

Valve timing needs to be as good as poss, not much to be gained but as much to loose so adjustable timing pullies.

Or just say sod it, do a bit of lightening then slap on a supercharger unit which is going to work much better than a turbo and would easily fit out of sight in place of the airbox.

Then you'll probably get to the corners first and go through them faster, probably go through motors faster too!!