360-1 Casting better?

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.