I think that there is a niche market for era correct performance parts, that's his ideia. Besides the one mentioned all the others have had the plenum mod. People Collect many things, just saw a post where a member collects camshafts. this could be applealing to a collector.
The small notch in the rear plenum is cast that way. Weather some didn't have it...that's it's own story..but I have 2 and both have the part # and the cast notch.
One is early and one is late. iirr.
