Lifter Bore

There is no correlation between the dash numbers on the casting number and quality - that's been debunked for years now based on factory info. That number is the core box ID for the main casting core. "-1" means it is the first run of blocks cast with it and succeeding numbers are revisions made on that particular box. These revisions were normally to compensate for wear as the core boxes were used because the sand material would wear the core and for minor engineering changes implemented during the production run. A single core box would do many actual castings. A '73 "340-1" and a '71 "340-8", and a '68 "340-3" will have small production differences but no inherant improvement in casting quality based on the dash number or year of casting and no improvement in machining based on year of production. I'll also add the T/A blocks used a unique main webbing core in order to get 4 bolt mains if so desired later. So they are identified as "T/A". Otherwise - same block and cylinder casting cores.
They all may suffer core shift and porosity and any block machined by the factory was done to an average level of quality. That means 1/2 were below average... I have yet to find one that was done to "above average"...lol.