Front Spring Rate Options:250lb- 11” tall springs for drag race only. Serious lightening required.350lb- Small block cruise or drag race with lightening required.450lb- Small block cruise, big block drag race.550lb- Small block handling, all big blocks except drag. (Allows up to 2″ lowering)650lb- Small block and big block handling, autocross. (Allows up to 2″ lowering)