drum to disc O.E issue

so ive been shopping around for a front disc brake conversion kit an im noticing what may be an issue: most say they bolt to O.E 10" drums....my car has, i think, 9" drums all the way around (original 225 /6 car). so how would i get these kits to work? upgrade to 10" drums all the way around and then switch tio discs in front? do i need a new front-end or can i use the stock set up? HELP!