[60-66]

The K46 that's on your glove box door states K46 for the heavy duty air cleaner option. The part number off the air cleaner you posted shows up to be 64-66 10-30 Heavy Duty air cleaner, that's right out of the Chevrolet parts books. This air cleaner was also used on the 40-60 Series trucks according to the Chevrolet parts books. That's interesting, Never have I seen that air cleaner on a 1/2 ton anything. I have a similar air cleaner that runs the duct like yours on the firewall but I've never seen it in place. Thought it was always BIG truck stuff. Kinda reminds me of Chevrolets cowl plenum air cleaners from 63-69 on 409s and 427s. Guess it was a way of getting cold fresh air to the engine on these trucks..