Looks like I'm going with the stock rubber bushings....
After 2 days of reading, there doesn't seem to be any consensus on any bushing type. A lot of discussions even had mixed types - Poly in upper and rubber in lower, etc.... cold flow, squeaking, binding, deflecting, deteriorating, grease – no grease, graphite – no graphite, too harsh -not harsh.
I guess I'll go with GM's research dollars and stay with the stock material. If it doesn’t work – I can spend the dollars later.
If I had gone poly - I would have chosen these:
http://www.pfadtracing.com/products/...&search=&page=
Maybe the problem is I read too much. Just do it !