1965 was emissions in California. I was there.
They tried the back-dating requirements on older cars (I recall a Carter box on the inner wing of a 1950 Ford Fordor, and a PCV), BIG court case, Califreakingfornia got slapped back.
AT LEAST first PCV's in 1966, maybe earlier, like 65, as I remember seeing them (to wit: 1965 Fairlane with a 260....there is a funny shaped triangular bit on top of the inlet behind carb....leftover from when they were a cavity filled with coarse steel wool, plate bolted on top with a PCV valve screwed on).
Early on, hot air inlet for carbs, dual advance.....
Good thing they quit looking. They USED to make sure you were "stock".
ANY emissions controlled vehicle.....and I know this from watching it happen..change anything, $10K fine to the shop OR owner, and you HAD to put it back.
1980 Chevy, 350, blown engine, order out a long block, put it in.....unfortunately, casting numbers said 1970....$10K and put it right.
Dave