Unfortunately, you may or may not be spending money you didnt need to on another block. I have sonic checked over 400 blocks, and there is one thing that is consistent. There IS NOTHING consistent! ( the GM blocks are more consistent than the Mopars for sure) The ole MP rule of only .020 overbore is garbage. I am surprised any shop anymore doesnt sonic check a block,subcribes to that theory, and randomly has a customer assume a block is junk. Thats the shops job, to check and provide information resulting from proper procedure.Sounds like he ha d ablock he wanted to get rid of????

As far as the " good" or " bad" blocks, there is no such thing. The nickel content can be different, some blocks can be harder than others etc, but the only way to know if its good is to sonic test, magnaflux and or presssure test. I recently checked one of the vaunted " 230" blocks, standard bore. Customer paid ( i think) $300 for it bare. It didnt sonic test very good. Will need a couple sleeves to do it right. You just never know.

As far as core shift, yes, sometimes that rule stands true as to bore centerlines, cam tunnles, oil galleries etc. the problem is when you have a centered core, but how do you know if there is a thin spot or void in the casting on a cylinder. You will often find blocks that sonic well, then all of a sudden there are voids or bad spots, sometimes 1" round or bigger in a bore test. I actually cut an old block open once to confirm after deaming it junk. Sure enough, a very thin casting, along with rust, had thinned that area.

I think the shop could have done you better with a test first, but if he's your guy, then you have to roll with him. Good luck with your build..