see if you can find a LONG ROD kit or a stroker crank, shave the head to up the compression, use a bigger CC engine (500cc) different pipe,bigger carb,porting to the hilt, to do most of this your gonna have to find someone that knows two-stroke motors VERY VERY well and can do the work correctly for you. i would also do a search for HILL CLIMBING bikes since alot of those guys use 2-strokes. (they also use LARGE CC street bike motors etc.)
good luck
good luck