Engine ID?

trying to get to the bottom of what year engine I've got. So far there are several clues but we haven't been able to crack the code.
-We have blue paint. It seems to be lighter blue indicating "turquoise", but it's so faded and rusty it's hard to tell for sure.
-We have what we think is a '68-'69 timing cover/water pump (which came with the engine from the junk yard.
-We have the imprint on the front of the block (from behind the pow.steering pump):
M318R 06 13 1947.
-We have "2536030" and...

Engine ID?
Author: Rosco