Saw another post from a guy who has a 66 and wanted to add 67-68 booster. He was told to get a 67-68 off-set air cleaner and he found one at junk yard from a 250. Seems as though your motor was replaced? The 66 would not have the hole in cover unless the hole was added? Do you want to go back to 66 stock air cleaner/valve cover or add booster or leave it because it's neat?

Right is right, even if everyone is against it, and wrong is wrong, even if everyone is for it. - William Penn