in a EF when you using parts from DA everything fits no mods. the booster bolt up with no problem as well as the master cylinder and the proportinoing valve. the rear disc conversion fits perfectly. it is recomemnded to change at least your rear trailing arm bushing. it is said also to use the booster and master cylinder to get better pedal feel and response, and trust me its nice. in stopping in my car you could get whiplash from the forward momentum when stopping if you just stomp on it!