I didn't use their spring but did install the bushings. I have had very limited time behind the wheel since the install and since every part of the suspension is new, it would be very hard to give an objective opinion.
One thing I can say, these come with grease fittings and must be lubed. The sleeves come pre-drilled for the fittings and one must be very, very careful when you install the sleeves so you will be able to reach the fittings once installed. I purchased a set of leaf springs from NPD, #138 rating with a one inch drop. I had to remove the installed rubber bushings and then press in the G/West sleeves. I used some threaded rod and steel blocks to pull the sleeves in place. Sounds messy but actually worked very well. I drove a chisel into the opening where the eye at the ends of the leaf are formed. This reduced the pressure and made the puller work pretty well. The real pain was installing the sleeve in the rear subframe. a real PIA.