340 engine help

Ok I have a little more info on this motor. When I was oiling up the cylinders I took the numbers off of the heads. I was told to look and see if there was a J,U or X on the heads near the plugs, none of those anywhere. On the outside the only thing I can find is a number 26 embossed between the first and second plug hole. On the inside the casting numbers on both heads is 3769974 next to that is a smaller number, on the left head it's 1634 and on the right head it's 1214. The clock on the left head is pointing to 9:00 and the right head is 10:00. Then a little further down the head at the top is embossed 360 on both sides, and under that are the letters AAWJ. Next to that is a small #123 with a little arrow pointing to the # 2 on both sides. On the left head only is a big embossed L. Any Info on these heads will help. Also don't think it'e any big deal but he had AcCel 117 plugs in it don't know if this means anything or not
Thanks
Bob