FarNorth, Before we switch back to the engine ID info, I just wanted to add that after reading Mike B's input above, indicating that the "AN" designation is correct for a 1941 1 Ton, I can back his info up as both my 1946 and 1948 Master Parts Books say the same thing. Looks like the GM Heritage Chevrolet data file isn't 100% accurate.
On your engine ID, below is another extract from the GM Heritage site 1941 Chevrolet Truck data specifically for the engine ID info. The "AAF" designation does show in that chart as falling under all 3/4 Ton truck categories, which I would think may include your 1 Ton rated truck as we discussed that being the long chassis, but with lighter rated springs and the smaller 6 x 20 wheels. The info doesn't say the "AAF" is a 216, but in footnotes on the bottom of the page for the Conventional Trucks/School Buses and COE's, they got assigned a different model ID designation to them to indicate they had 235's installed as an RPO.
That being said, the best info I can find says your "AAF" engine is a 216. I did one more check in this resource
Chevrolet Owners Manuals. In looking at the 1940 and 1942 Owners books, both indicate that 3/4 Ton trucks were equipped with 216's. I couldn't locate a 1941 Owners manual to check that info to be sure.
Perhaps there is a fellow 'Bolter with an original 1941 Owners book that can look it up and confirm???
Sorry - Kevin beat me to the post button with his answer.
