About 10 years ago, my dads 67 Hemi GTX needed rear springs, as they were old and sagging. Rather than have them re-arched (which we should have done) we decided to put new MP springs on them. Once installed, they laid flat and we had virtually no difference in height then when we started. After all the work, we just left them on there.

I later learned to order from ESPO (Eaton Spring) and to order 1" over stock. Never had a problem with spring height after learning about them.

You should call them and talk to a tech, they will know exactly what you need.

Chris