I've got an '05 yz450f and have read about different mods I can do to increase my speed. I've dropped my rear sprocket to a 48. I've ordered, but haven't installed The Big Gun Rev Box. I've read about swapping to a 5 speed tranny as well. I ride the dunes and trails only and just don't have the top-end speed I want. (mostly just in the dunes) What should I do? As far as swapping trannys goes, does anyone have a parts list?