No idea?? All searches I did on it came up as 71 - 73 340 passenger side manifold. I didn't pull it from an engine, it came with a bunch of parts I bought.
Part # is clear, 3418623
Looking here on TTI's website for casting numbers, it comes up as passenger side for '67 - 76 A body, 62 - 79 B body, and 70 - 74 E body. NO mention of truck.