Thanks all for the quick replies.
I did not see anything beside the starter. (Maybe have to revove starter to see this?) The engine # on the data tag, drivers door post is an exact match (well, T73-5213 vs T735213) so this is the original engine to my canadian model 1100 (specifically model 1143, a 14,000 gvw truck)
The casting number on the block, forward of the fuel pump is GM 5843350. Casting number on the head is GM 3701887.