Hi mdkd,
The Buick finned aluminum valve covers came with the factory dual quad option. Yes, the rear AC compressor bracket from a dual quad setup is needed to clear the aluminum valve covers when you also have the dual quad intake manifold. There is no factory rear AC bracket that clears the aluminum valve covers and also bolts in the correct location on a single four barrel carb manifold. I've seen this problem solved in different ways. One, cut the arch larger in the single carb bracket to clear the aluminum covers. Or, cut into the aluminum covers fins only just enough to clear the rear AC bracket. Or probably a combination of the two alterations. It might be best to use your chrome valve covers that came with the dress up kit.
Hmmmm. Wasn't there someone that was custom making an AC bracket just for this kind of set up? Or is that my imagination.
John