Sorry about that James!
I got my tongue and my brain all caught up in the thought of that 289.
I am also sorry that everyone keeps generalizing there answers.
That object is whats called an Air Filter Assembly.
It's purpose is too house the Air Filter Element and too cut off cold fresh Air through a valve called a Thermac: which detours warm air from the Exhaust to the Carb. for better fuel atomization.
If you do like this answer please give the 10 points to Therick6
Hope this helps