Way back when (about 15-18yrs ago now !!) I bought a set of MP super stock B body springs for the 70 Sport Satellite - they only lasted about a year, before they started to sag and then get to point they were arching other way !!! Not sure if Mopar Performance springs have gotten better since then, but I took the original springs in for a re-arch and add a spring . . . have been on the car now for 8 or 9 years, and no sag at all.