Yes, that's it. It one of those things that get tossed. It doesn't appear to serve any purpose but Eagle1 pointed out that it probably shields the choke from wind in order for it to register correctly. I'm not sure how many years they used those for. I know the 78's with a 400 had them, at least the W72 engine anyway. I'm not sure about 79, but I would venture to guess they were used on the W72 cars.
Edit: It looks like the engine above is not a W72, so I guess it came on all 400's in 1978. They seem to be hard to find, but I haven't really looked for one.