I have been doing some research on the suspension set-up i just did (KYB AGX/Pro-kit) And from what i have been reading, people seem to get a nasty squeek from the rear and have isolated it down to where the rear springs touch the shocks. I have read somone took a toilette plunger and cut a ring from that to put between the spring and spring seat but when i did my suspension the other night, I found that i could use the old front rubber spring isolators from the bottom on the small side of the spring, cut off that little nubby part, and put that on the rear shock spring perch. Since there is no GM part listing for a rear lower spring isolator and since i replaced the front sets anyways, i found this to be an easy and very effective solution.

I'm not sure if anyone has done this yet but it is working very well.

By the way, the ride on the AGX/Pro-kit with eibach front/rear sway bars is AMAZING!

Yeah. It's been covered before. You're right. Just get GM front spring isolators and use them on the rear.