The valiant emblem on the T shirt is 62 to 66 so you nailed it. I always assumed they used that emblem all through the 60s but it is not used in the late 60s
The 60 and 61 were the same emblem but instead of red and blue it was red and grey.
67 they ditched that emblem all the way around and replaced it with the plymouth rocket (so I call it, but I don't know the official designation)
The plymouth rocket appeared until the 71 model year and after that only the cursive "valiant" emblem was seen.
Oddly enough 63 had a "by plymouth" emblem on the tail gate or rear deck and no where else on the car does it say plymouth, so it wasn't a plymouth valiant, it's a Valiant by plymouth.
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