http://www.ebay.com/itm/REAR-LEAF-SPRINGS-70-73-CUDA-CHALLENGER-2-LIFT-/280782965904?pt=Vintage_Car_Truck_Parts_Accessories&hash=item415ff80c90 I like these bad boys. Low deflection, rear shackle angle is perfect. I think 3,800-4,000 lbs rating. But 440's are heavy and set back more than a LA. These are the best, and I tried the E body Mopar Perf. 440 stock made in Mexico, and within a week of driving and one drag outing they were flat, with the rear shackle almost going over center due to the rear angle of the shackle. Instead they flexed back ward in the rear segment. The stock snubber was only 1.5" away from the floor, unloaded. The bias was not enough to count for anything.
I had the 3600 E-Hemi SS set first, and sold them too, for not enough float on the street. They had the 6 thinner leafs. They give in too easy on a bump. Plus, I went to the DrDiff offset hangars and 68' housing. Now the car digs at the drags with good separation and won't move down much when loaded up.
The new 2800lb A body set made in Mex. SS, I just got, are thicker than normal and worth the $ for the 1968 cuda and worked like Sox and Martin's car, hammering the axle down. Just enough lift for larger 28" tires/slicks. but not enough for the 29", I found slight touching at the back of the drivers side wheel opening due to the bias making the leaf straighter, thus longer and further back.