(Chuckling at Vince's posted photo and Bentley's 'wheels'... )..
now getting serious, and expanding a bit on the previous responses to the OP...
Most people 'restoring' their Rallye wheels only ask (or are concerned?) about the front and back faces of the wheels, but if you truly want to 'restore' your wheels (as in restoring to factory original new condition), you also need to 'totally cover the wheels in the black primer .. ie. JohnZ states the wheels were immersed in a vat of primer'... meaning the front, back and rim areas of the wheels are totally coated - heavily- with the black primer when they are removed from the vat.
Given that you and I don't have a 50 gallon drum of black primer or black paint to 'dip' our cleaned, stripped and prepped wheels into, what we can do is load up our paint cups with your favorite black chassis or reconditioning black paint (I use the GM version), and apply a very heavy coat to every bit of the surface, front back and rim area. The silver paint is only applied to the 'front side' (as described in John's paper) but no attempt to mask the other areas was done, so allowing the overspray thru the holes onto the back side is accurate and appropriate.