Ramblings:
If I wasn't lazy, I'd help design a shirt. Instead, I will pitch an idea.
One shirt for the coupe-only models, and one for the multi-layout platforms
It would have a lot to do with overlapping side-view silhouette outlines, using black where they match and separate bright colors where they differentiate. They would be lined up at the wheels. Cars with wheelbases that don't match would only be lined up with the front wheel.
-The Coupe shirt would need 5 colors: GP, 2+2, Cutlass, Regal, Monte SS Aero to keep it simple yet inclusive. (Excludes Regal header panel change, GNX &
H/O, Monte, Monte LS, and std Monte SS. Would all be too hard to make stand out from the others) Due to the way these models look, the design may look cluttered, but that could be helped by separating each silhouette vertically and "listing" them down the back of the shirt. (the other 3 Montes could then be included this way, as they are still visibly different in ways) Also, thanks to having only 1 body type, windows can be included. The door universal door window in all-black, and the quarter window showing each difference. (Olds with the curved corner, Regal with the flat bottom, GP & SS with their larger "angular" shape)
-The Multi-layout shirts would need 6 colors: Sedan (universal), Wagon (uni), Ute (Elky/Caballero), Malibu coupe, Fastback (CenturySportCoupe / ButtlessCutlass) and Grand Am. (Choo Choo excluded.) This design would be far more effective since the changes between these cars are far more drastic and would be far more visible at a glance. And if the "list down the back" idea from the coupe shirt is carried over, perhaps there can be small text underneath each car silhouette stating each model. Example: -Wagon silhouette- underneath, "Chevy Malibu, Pontiac Safari, etc."
Under that (talking about the front again now), a line of reference text. (Reference to G bodies, jack of all trades, etc.)
And lastly, under that, from left to right, the logo of each participating GM brand. (4 or 5 depending on the model. Can't forget 'ol GMC now...)
I didn't realize just how huge the list of G-bodies really was until now.
Anyway, if I still had Adobe Illustrator I would maybe try this. I have GIMP but idk if it does vector drawings.
EDIT: I may still try and make a proof-of-concept.
EDIT: Just realized I've forgotten the '78-'80 coupes. There are over 18 visually distinct G bodies.
😵