Which parts?

I rebuilt a front end with poly and it was too stiff for everyday use. Within 3 years the pot holes in Detroit had destroyed the bushings. I rebuilt it with the regular rubber bushings, and it was a softer more comfortable ride and lasted longer than the poly.

Also, be careful of the upper control arm bots in the kits. When I bought a kit, the bolts had the flat for the washer all the way down the shaft. The original style bolts only had the flats for the washer down the threaded part, not the whole shaft. I prefer the flat only down the threads, not the whole shaft. Making the whole shaft flat decreases the cross sectional area of the shaft, making it weaker than a fully round shaft. Make sure whatever bolts that you get have the flat only at the threads.

If you want a stiffer suspension for handling, then go with the poly bushings. If you want a smoother ride, go with the OEM style rubber.