Some questions & some opinions (formed with less knowledge than that of many others) here, but no attacks or criticism intended
Were blocks cast in Canada? Model A's going to Australia & New Zealand were "manufactured" in Canada and shipped out in knocked down form. If blocks were cast in Canada, how is the SCTA keeping them from being used? Can the SCTA prove that blocks were cast in Canada or Britain (innocent until proven guilty, right?)? Perhaps British blocks were shipped from Canada. If a Canadian (or British) block is functionally the same as an American block, I don't think there should be a problem.
Ford made replacement Model A (and B?) engines and blocks thru the '40s and they made Model A industrial engines even later, I believe. Are those being excluded? If so, how are they being distinguished? (Hint: 10 seconds with a die grinder removes the one distinguishing mark.)
The Russian blocks are almost undoubtedly of poorer quality.
The problem as I see it was the post-war German engines that came in the Ruhr trucks, aka G28T. These were "improved" primarily with full-pressurization and insert bearings rather than babbit. I suggest that a fresh G28T block is more expensive than the typically updated A or B block and that nobody with the possible exception of Shug is running unpressurized and on babbit.
Seems to me that policing is a problem, mistakes can be made, mentions of cheating have been made in the past (although I see no advantage in using a block cast after 1934).
But, the rules are the rules and that is what we work with.
Vertex: blocks can be shipped via UPS, but it looks alike about $450 from my west coast address to Europe. Try contacting Belcher Engineering in England, they might have some insight on the block question.
Good luck.
Mike