Sorry Greg, I don't have measurements. It was a local race car builder that made them, so he did all the measuring. I do know that he turned them on a lathe, and it cost just under 400 Canadian. I consider it money well spent, because as I said, it virtually eliminated the shudder. I don't know if Delrin is available in a different durometer, but mine seem essentially solid, which is fine with me. Perhaps vibration would be more of an issue in the front suspension, but I have nothing negative to say about it in this application.
Yes, they're the large, "butterfly" shaped bushings that attach to the axle on the 700 series. Of course, having rubber bushings that large gives a lot of opportunity for excess flex.