Gene, I think this is a timely thread, with the other recent thread about i.ding flathead blocks year by year bringing out so much variation, and being added to continually.
The Canadians certainly did a few things differently, but Robert Dip's raised intake 37 block is unusual even for Canada! I have a Canadian 37-38 block without the whelch plugs in the pan rails which is also an oddity....nothing in Fordland is ever gospel.
However, I think the major pre war difference between the two sources is that from the introduction of the LB block [in late 35-36?], ALL Canadian blocks have featured a 5/8" dia hole at front of block, in pan rail, on pass side [US], which readily identifies the engine as having shell main bearings, actually, there is another 5/8" hole present at rear of pan rail also, in front of oil pump, but one needs to remove oil pan to observe this.
No Canadian blox had numbers cast into them until 38.
I have 38, 24 stud blox with no numbers, these blocks share the same crankshaft etc, as the earlier 21 stud stuff , but also have 38 blox with 81A cast into them, which have 24 studs, the bigger main bearing journals, the later crankshaft with the longer snout and are still 221. Likewise, all 39 Ford motors have the number 91A cast, the Merc's 99A. All pre war Canadian Flatties from 36 on, at least, would appear to differ.
