What even the GTS "experts" are not always aware of... There are two different large diameter unsilenced aircleaners used. One was used for '67 383 engines. The second one with a revised/different top stamping can be found on some of the earliest '68 383 engines, up until production switched to the MUCH MORE common smaller aircleaner also found on '69 383 and 440 GTS cars. I feel I'm correct, since I have one of each to place side by side and note the difference. Why Chrysler tooled up a different top stamping for '68??? I don't have a clue.