The 1/2 inch thick spacer on one side is a great idea. It is very hard when building a car, especially one with exposed underpinnings, to get everything exactly the same side to side. We have to tweak things sometimes to get them to look and fit right.

I would also be curious what kind of suspension setup you have, because if something like coilovers with a panhard, you should be able to adjust it over that far.

Don