The DECAlink™ Independent Rear Suspension features no compromises and exclusive Detroit Speed suspension geometry for superior handling and ride quality. The IRS utilizes modern CV axle shafts and hub bearings, keeping suspension loads from being transmitted through the axle shafts. The DECAlink™ IRS works with an original 17-spline differential assembly or a Hammerhead 12-bolt differential. No body modifications are required on 1968-79 models while the suspension is offset inboard for additional tire clearance. All suspension link lengths are adjustable and the kit has adjustments for rear anti-squat geometry and roll center height. The suspension points are hard mounted to eliminate stock rubber mounted suspension deflection. It comes with forged in the USA Detroit Speed aluminum uprights and a two-piece cast aluminum/steel cradle assembly which eases differential housing removal. DSE/JRi "Detroit Tuned" Coilover shocks/springs allow spring rate tuning and ride height adjustments. The kit includes a rear anti-roll bar and uses OEM cross-axis pivot bushings at all pivot points. The kit also includes Torrington bearings and a spanner tool for easy spring height adjustments. Base Shock The DSE/JRi 'Detroit Tuned' base shock is a 'pure blood pedigree' racing shock in its most efficient form as a non-adjustable unit. Although non-adjustable, it shares all the increased dynamic responses of all the JRi adjustable models while providing excellent ride quality on the street. Rear Spring Rate: 550lbs/in Rear Spring Free Length: 8in The axle shafts are rated to 600Hp, and the factory 17-spline differential is recommended to only 400Hp. Upgrade to Part # 041741DS for the DSE 30-spline differential if you have 400 to 600Hp. Upgrade to Part # 041742DS if you have more than 600Hp.