Ray, you will know this right away and I never remember. Does it have the correct hood, or is 73 the year that it's not supposed to have the grilles/vents at the back of the hood?
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1966 Strato Chief 2 door, 427 4 speed, 45,000 original miles
1966 Grande Parisienne, 396 1 of 23 factory air cars
Cowl vents came on all 1973 hoods and most 74 hoods, by 75 no vents at all. All service replacement hoods even those date stamped 1973 have no cowl vents.
The dual scooped hood was only standard on 1973 GTO and the 1975 LeMans GT package included the hood, so in effect it was standard on the 75 GT even though the GT was an option.
Some Pontiac litertaure suggests the hood was only optional on two door cars but there are PHS documented examples on 4dr. Grand Ams and Lemans Safari Wagons.
I ran into a fellow at California's Cruise who bought a 1973 Grand Am used from Dean Myers Chevrolet in 1981 and prior to delivery he had them get a service replacement hood and paint it to match, it has no cowl vents.
I read a lot and talk to the few guys in the US who know about these cars. Unlike the 64 to 72 GTO/Lemans/Tempest there are only a handful of "experts" on the 73-77 Pontiac A Bodies and toss in Oshawa production on these cars too, very few "experts" even know about that.