[David_Hayward (RIP)]

The casting number 839253 appears to be a Canadian 1940-5 Block. I have so little information on the MR-prefixed series but it seems that they were fitted in C8s, but they stopped being assembled in late 1941. The C8A series in effect replaced, and the engine number appears to relate to a truck built around May 1942. This leads me to suggest that the engine is out of a C8A, and was transferred to a replacement block at some time. However, I may be totaly wrong!