360-1 Casting better?

Garrett Ellison said
A lot of good information here, much thanks to everyone for sharing the experiences. This brings up a question on a particular dash series number... 318-3. Mentioned in the MP manual as being a heavy duty motor home and industrial unit with a premium crank. Would this have been a separate mold setup for extra wall thicknesses? I’ve got a friend with a 1982 -3 series number block (reman from jasper) that appears to have been cast as a reverse rotation marine block. We haven’t weighed it yet but when compared to a regular 318 block the cylinder bores are obviously much thicker on the minor thrust surfaces on the left from the front side of the bores. I Also know of several early 318 truck blocks (68-72) in -5 and -7 that have been sonic tested and can go to a 4.1 inch. Definitely the exception instead of the rule, but they are out there. It makes me wonder how high the dash series ran in one off production blocks like the 340 T/A before the end of regular production before it went to an over the counter piece.
I’m not going to say it’s completely right (the sonic tester is be all/end all!), but I know some who look for the highest possible dash numbers so they have the latest revisions.

Not saying they did not do that, but if the factory was building production engines and using standard stock sized pistons, why would they make the cylinder walls thicker for HD applications. The strength in an engine block comes from the thickness of the top and bottom decks and the main bearing bridges.
I can see thicker walls being built in for a block that had a racing application, to allow an over bore to a bigger piston. But to track those from casting to machining to assembly typically the special part would have its own part number. Part numbers are used to differentiate similar looking parts that are actually different. Pattern numbers only indicate the tooling that was used to make the mold, which makes the exterior shape of the casting, the pattern would have very little influence on cylinder wall thickness, as cylinder wall thickness is set by the water jacket cores and the main body or what was called the barrel core.