What kind of blower are you using? Inlets ,outlet,highhelix? The set back deal is mainly for the front discharge blowers. They have an outlet that is a small delta (pie shape).This pushs the air all to the front of the case and it comes out at near a 45degree angle. So it pushes more air to the front clyinders and less to the back if monted in stock location.The newest set back manifolds set the blower way back on the motor. Keep in mind that the snouts for a full set back are very expensive( $2500 and up for just the snout).There are other options.Depending on what you plan on running a full set back isn't worth the money in most guys opion.Hope this helps