a drop in cam would be a start. stage2 or Hrc. if you want topend. Go with the HRC.
get a full exaust system on there. theres a few good ones out there. N-motion,ESR,Dasa,etc..
some port work and a high compression piston with 13t sprocket would make that bike scream.
i have a 450r as well, its a duneplay bike, with a stage2 cam, esr intake, yoshi exaust, elka shocks, houser arms, 39t and a bunch of replaced boltons. going with a 12.25 compression venom piston to run pump gas.