[Adam]

I looked into exactly those 455 fender emblems (because I wanted a pair), It turns out they came stock on the LeMans with the 455, not the Grandville.

And all 71-74 Granvilles had the 455, while the other big Pontiacs: Bonneville and Catalina, had either the 400 or the 455 those years - and Bonnevilles and Catalinas with the 455 got one on the grille. But the grille emblems were 71-73 only.

The 455 on either the fenders or the grille might have been something you could special order on a Grandville, but it didn't automatically come with them (even though they all had the 455).

At least that's what I came up with after googling it for an hour or so.