I would only replace the bearings that are worn out or damaged. You can upgrade to the '07 or newer crank to get 449cc, $218 plus shipping at cyclepartsnation.com. Also contact JTATV in the sponsor section to upgrade to the '07 oil system. I am getting set to re assemble my '05, 97mm CP piston, '07 crank, full DR D system, cam mod, k&n filter, YZ clutch and ported head. All of this = 468cc MONSTER.