engine id help

i think i bought a 68 olds engine but not quite sure, on the back top of engine by bell housing this is whats there.a dot with arrow pointing to it followed by 2 dots on top of each other,then 455,,under 455 is 1241735,,then beside that a big 8,,then beside that gm sideways..any help is appreciated..

[70ragtop]

I really need the number cast in the front of th engine between the front intake seal and the water pump, on the top of the block just to the right of the oil fill tube. it should read 396021 F. The number stamped on the pad near the number one cylinder can also be helpful.