The gauges are available from many outfits such as Autometer, or Stewart-Warner, and in kit form; you just have to weld in a bung in the header collector(s), and wire it all up. That one for the OBD II cars is slick, but not the deal for a traditional hot rod. As for your three deuces, if you are running progressive linkage, just disconnect the secondary linkage and tune on the center carb by reading your plugs; then figure out where you want the secondaries to come in, and set the linkage accordingly. When you are going WOT, the AFR goes out the window anyway, unless you're going to be running that way for a very long distance or time.