i have a 72 duster that i am running 275/60-15's on .i have torque thrusts 8 1/2 wide...I need to raise the rear to keep the tires from rubbing...my current 30 plus yr old springs with outdated air shocks are not gonna cut it...My questions are...do I buy a new set of hd"s from mancini? Do I buy a set of superstocks???.I need 1-2 inches over what i have now( stock 340)..any and all input welcomed...