Atleast 1500. you'll have to extend the chassis, panel beat the lip, weld the horn cast and make the legshield broader. not to forget you need 8 inch lug-type vbb wheels, hub/drum and fork. don't do it. it's never going to look 100% like a VBB and the money you spend on it cannot be added to its market value. I would keep it the way it is, the PX has it's place in history. keep it real.