you can lose a lot of weight by using an 04+ subframe. the 03 subframe is steel. starting in 04 they're aluminum. is there a reason for using an 03 subframe? the subframes are also slightly different. i'm pretty sure you'd have to use a newer seat. wera doesn't allow subframe mods for superstock. i'm pretty sure ccs doesn't have any subframe restrictions, but i'm not 100% sure.