The lower control arm was designed to be a press fit with the rubber bushing. A poly bushing does not have the ability to hold tight to the shaft and will allow fore and aft movement. Many will say the torsion bar and the strut rod will prevent any movement. But, I don't want to trust it. I have used Poly bushings every other place in the front end and it seems to work great. The problem with the factory rubber bushings is they would wear heavily over the years, get oil soaked and had to be replaced more frequently. It is not an easy job as everything in the front end has to come apart almost, then the bushing requires a press and the know how to remove and install without damaging the control arm or the new bushing. I would not see any benefit to poly here at all, put new rubber in and call it good.