From those pics it looks like there has been some machining done to turn it into a single plane type intake? That's kinda thin gasket surface. It does look original to me though but I am definitely not an expert on Shelbys.
I had an over-the-counter Shelby dual quad intake that was about the same vintage. That's exactly how the edges looked and I can tell you now they don't work well. Turn a modern Holley 4 barrel carb over and you'll notice lots of vacuum passages that are cast into the baseplate that would be closed off with a modern, thicker-walled intake. Those passages ( PCV for one) are exposed with the thinner-walled intakes and create a huge vacuum leak. Neat intake, but if I wouldn't run one.
How is it ruined? I think anything in Edelbrock's catalog will out-perform it before or after the machining was done. If you wanted it just because it's a Shelby manifold, please see my previous statements about how modern carbs can't be used due to the thin sealing lip, as opposed to modern intakes which have a large, flat sealing surface. Reproductions would give you the same look without the headache. Been there, done that.
Ran one on my 65 Shelby replica for years and loved it .If the throat hadn't been opened up a Ford spacer plate works perfect with any Holley .I used a 429 spacer plate ,it is only a bout 1/2 inch thick and a solid block so it doesn't hit the hood or create a vacuum leak .