you want the best go 16 450 or 17 , and if you are feeling rich go 17 kx250f , the older alloys frame are ok but you need different off set clamps and longer pull rods on link to bring them up to par in the handling stakes plus you must make sure the frame tube mods are done very good as there been a few breakages for what ever reasons myself i would do a kx250 04 2t or something along them lines as they handle good and are easier to do. there no advantage in alloy frames , i would use a steel frame and update the suspension and brakes etc.