yep that 30.4 is really very short, the 39.85 should be better, don,t forget to factor in the distance from the axle centerline to the top bar on rear houseing bracket. i would stiffen shocks at about half, for a start and go up or down from there, prob... up. watch any bouncing.. or listen for any waa waa, of the engine. heck i can,t belive i typed that, :? anyway good luck and keep posted.