I would look under the head where the exhaust heat crossover is for the casting number. You said you have a 360. IF those actually are 318 heads, then they didn’t come stock on that engine.
I'll check it when they come off and update the post. Aren't the blocks pretty much the same for a 318, 340 and 360? I thought the CI difference was internal and you could do some different head/block combinations. They're stamped as 360 and the engine ID was a 1970 360 from the Windsor plant, so I'm not sure what to think at this point.
