Originally Posted by JimBlake

Sometimes they won't notice a bent rim unless they're looking for it??

Wheel spacers just change your track. I don't think they'll do any good for your vibration. Centering rings just help hold the wheel centered. The center hole is supposed to fit close around the raised part in the middle of the hub. When the lug nuts are tightened properly, I don't think that's your problem either.

Find a place with a Hunter GSP9700 (URL below), that can measure road-force variations while it's balancing your tires. Maybe the tire itself isn't quite right??
http://128.242.141.111/index.cfm