I bought a spare set already modified for aftermarket roller rockers to play around with to hopefully get a similar appearance. I really have no idea how this was done....sanding to bare metal and polishing/clearing, paint, strips of a chrome/polished material over the top of the ridges of the stock covers?

 

A sharpie and alot of patience.

 

lol, I've got one of those silver sharpies in a cup to my left right now.

 

They were painted, then the ridges were touched along the tops with a file. I've done a couple pairs of Ford SB covers like that (old school "COBRA" covers), it works well, and looks nice

 

Sorry, don't know what you mean? You mean the ridges are metal? Or the ridges were painted? Some of the ridges on the valvecovers just stop and become flat, so they must have been carefully rounded off at that point.