Modern,
You are saying that the bolt on wheel spacres would then allow me to choose from a lot of wheels, but without them I must have the 4X4.5 wheels. If that's the case then I am looking at some real problems trying to get my Z loaded to bring home. What is the offset you mention? I don't understand it's importance or where something is being "offset"? Finally, I assume that the 4.5" measurement is the centers of the bolts rather than the outside.
Please correct me if I am wrong.
Scott