Poly does work well, Even with many motor swaps. And cost less.
Poly is harder the rubber and won't wear or make noise for cradle bushing use.
(I hate poly in control arms. See my Cave, Bushings
I think my cradle kit, black poly, is 10+ year old and no problem. I have my cradle out for other reasons and looks nearly new.
If you want rubber... No clue.
Moog and others don't list cradle bushings.
Can't get them thru GM parts dealers that I've seen.
Dr. Ian Malcolm: Yeah, but your scientists were so preoccupied with whether or not they could, they didn't stop to think if they should.
The Ogre's Fiero Cave (It's also at the top and bottom of every forum page...)