Early LA 360 Blocks

That was me suggesting you to do a search, where there are in depth facts by me and others for you to read through. I apologize but I can't see how you define that as condescending. You said have your own ideas on the subject and perhaps you are simply receiving the info from the position of "prove me wrong". I don;t care if you believe me or not. I generally just try to help. There is a lot more misinformation than fact on this subject because not everyone has the experience over the decades, the right equipment, connections, or knows how to use it properly. That's not a condescending opinion on my part. It's just what I've found over time. It's also not a problem for anyone who wants to add to the discussion to do so, regardless of thier background. Now so you don't have to do the search... Here's some truths I've found over the years:
Concerning 360 LAs -
Truth - they are cast of a better quality iron. "High nickel" is a term usually reserved for GM or Ford because historically they use softer iron for production blocks than Chrysler. Studebaker has the highest nickel content and hardest blocks I know of in a gas engine...
Truth - The first year LA 360s were cast using the 340 cylinder cores. This was a simple idea to use existing materials on the "new for 71" engine. The resulting smaller bore means they theoretically have thicker walls. This was changed for 1972, my guess is to use less iron in each casting.
Truth - Mopar's casting quality sucked. It sucked for everything, all displacements, right up to the Magnums. So the fact they used a 340 core, and good iron, didn't stop that core from shifting when they were poured.
Truth - Using a good certified sonic tester, on more than a few blocks, is the only way to find these details out for yourself. I happened to buy my own good one, and paid to have them train me on how to use it. I have tested for shops, racers, customers of mine, and friends locally for 9 years now. I've tested a variety of makes, but I've been building only Mopars since the mid 80s.
Truth - In the mid 70s Chrysler changed to a low quality iron. I believe it was around 1977 but that's info supplied to me by a shop that was rockwell testing various year blocks for a circle track program they have so call the year en estimate. Around the same time as this material change was made, the blocks seem to have gotten generally thicker in the major and minor thrust, when not affected by core shift. This is true from later 70s to the Magnums. A point of interest on what MRL posted... The Magnums have the larger main feeds, but so do the later roller 80s-91 LA 360s. As far as mods, enlarging the main feeds only requires a long drill bit and a steady hand. I do it on all the builds I do.
Truth - Visual inspection of any kind is only as good as the eye and the lighting. Sorry to disagree with Stroker but anyone that knows about castings or machining will tell you your eyes are the last thing to use to test. This would be why I also own a magnufluxing setup and why the better sonic testers are certified.
Truth - The most consistently well-cast 360 blocks I've tested are the 89-up 360s. I have not tested many Magnums. Only one, which was on par with the later LA 360s, so I'd agree with MRL there. As a point of interest, the best 340 blocks seem to be the 72-73, not the earlier ones.
Truth - The fact that the factory wanted a certain result has little influence on the production quality. This is also true for the "230" 400 B wedge blocks that were actually supposed to be thicker... but still suffer from core shift. Just like the early MP Hemi and RB blocks, and the early production 59° MP small blocks that were unable to go more than std bore. I have several 422s running around in blocks that went .060 over and had meat left over. I've also seen stock 340s that needed sleeves due to cooling jacket rust that caused pitting and thin spots that were thinner than .070" at std bore and a little wear. I've had numerous blocks that got one or two sleeves to make them passable. That's because 40 years of use, the elements, and foundry's lack of quality control created thier own truths regardless of the intent of the engineers.