360-1 Casting better?

Yeah, it's not a "pour order" number. The term is tooling revision number. It was to track repairs and revisions to the mold, not the pour. And according to every source available, there would have been multiple different tooling revision numbers being poured at the same time. Seems pretty clear. If the factory were going to track any number at all, it wouldn't be the order the block was poured in. Maybe the number of times that a particular mold was poured, sure. But that wouldn't tell you anything about the quality of the metal in the block or core shift.

More importantly, why would the factory or the foundry care what order the blocks were poured in? It would make no difference to them at all, the block would either pass QA or it wouldn't. The tooling revision number would matter though, because that would be the way they tracked their tooling and determined when it needed to be replaced because of wear.

And here's the real kicker. That number is on the mold right? Well, that means the number is on the mold before it's poured. Core shift happens when the mold is poured. Which means, that number literally can't tell you anything about core shift. It's there before the pour even happens. Even if it got a better pour order, that doesn't make it immune from core shift.

Doug Dutra talks a bunch about the casting process for the /6 engines here. https://www.slantsix.org/articles/dutra-blocks/slant-blocks.htm Couple of interesting points about the molds and the cores that went in them, which again, would tell you any number on the mold would be irrelevant for something like core shift.

"Let’s review what I know about how the cast iron SL6 blocks were made, namely the sand casting process. In the process of producing the "Dutra Dual" cast iron dual exhaust manifolds and the aluminum Hyper Pak intake manifold, I have become quite familiar with this type of casting process.

The RGFC blocks were cast 2 at a time, in a single sand mold made up of a cavity "rammed-up" into a box of "green sand", with several sand cores added, which create the hollow sections of the casting. The blocks were cast camshaft side down, crankcase to crankcase. Each mold cavity was loaded with over 20 "cores" made of baked oil sand. The major cores formed the crankcase, the cylinder deck-bores-valve tappet chamber, the water jacket, and the front and rear of the block. The main bearing webs and the crankcase pockets were made for both blocks by 3 large cores assembled together. The core that forms the front bay of one block forms the rear bay of the other, in other words, each end core formed the water pump scroll and the timing chain cavity on one block and the rear bell housing flange on the other. The water jacket cores were assembled to the crankcase and barrel slab cores using core wires. After the small cores for the fuel and oil pump pads are placed, the crankcase / water jacket / barrel slab core assembly was lowered into the outer sand mold and then the end cores were added to hold everything in place
After all the cores were set in place, the mold was "closed" with the top half of the outer cavity mold. 3 water jacket "venting holes" per block allowed hot gas and steam to escape through the top of the mold. These holes along with 4-cored holes in the cylinder deck were used to shake out the core sand after casting. Later blocks saw 2 more "venting holes" added to each block (5 total). These gas venting / "shakeout" holes are the ones we commonly refer to as freeze plug holes.

The mold was closed and poured. If everything was done right, out would come two SL6 block castings, ready to be cleaned & machined. Now that you see how all these cores were individually made, assembled and loaded into the mold, you may have a better idea of what the term "core shift" is all about. Core shift can be caused by poor core placement in the mold or the cores might move or "float around" when the molten iron is poured in. Either way, you end up with a casting exhibiting uneven wall thickness. Remember, the block is lying on its side so core shift will usually result in the cylinder walls being thicker on one side of the bore than the other. This situation can cause cylinder wall distortion or failure, especially if the block has been over bored by a large amount. The relative thickness of cylinder walls is usually thought to be the most important aspect of block selection."

He also talks about the rough castings and "sintered sand" and a few other things in the article I linked. Great knowledge on actual engine casting techniques.