Replace them with rubber bushing. www.rockauto.com or you local auto parts store will have them.

The rubber bushing is pretty thin anyway. Not a whole lot of area to move around in. And the poly will transmit more road noise.

If you are doing a bunch of handling upgrades start considering the poly. But for a mostly stock suspension setup don't bother.

Poly lower bushings can be tought to fit right. You have to save the old outer shell of your old rubber bushing. If you allready removed that, you'd have to put in a new bushing, push out the center, and destroy it leaving the outer shell. Even after all of that, it can be tough to fit the poly lower bushing. I had to grind the OD of mine to get it to slide in. I think some of the outer shell vary in thickness and can change shape when getting pressed in.