I'm thinking that probably the best source of info on where to find casting dates on your Canadian 235 is going to be from some of your fellow Canadians that own one or more.
There is just really very little resource information online on Canadian units, even though I believe they manufactured a whole pile of engines over the years. Your previous pictures showing the "casting code" 3837004 GM just above the starter location is the first one I can recall seeing in this spot on the engine.
One thing that may help a bit (not so much for the block, but for the head), check the head under the valve cover on the drivers side towards center. That seems to be a fairly consistent place for at least "head" casting dates to be found. The casting code number is normally just outside the valve cover seal surface, same drivers side central area. IIRC, you said previously that you had an "848" head, which is known to be used on Canadian engines, both 235's and 261's.Otherwise, maybe time for some really bright lights and taking some random pics with your phone on both sides of the block. Particularly down along the lower sections of the block just above the oil pan rail surface.
Post some "suspect" pics and we can try and help further.
Dan
Edited to remove assumed info on my part - Sorry!
