can i use a 450r rear shock on a 300ex? or what kinda mods would have to be done? looking to give my girls 03 300ex a some minor upgrades with out braking the bank

well, the 300 uses no link, and the 450r uses a link in the rear, so the 450r would not only probably be way too long, but the reservoir will be in the way, if you turn it so the reservoir is on top, then the airbox/boot will hit it.