400 B block

There are mid 71 casting date 400 blocks that are known as cold-weather or "230" blocks because of the part number of them. The only difference is the thickness of the cylinder castings... in theory, they should be able to be bored .060 over and have plenty of meat left. That myth was debunked byt the use of sonic testors, that found they suffer from the same core shift issues all mopar blocks suffer from (Even the MP offerings) So if the planets align, and you get the 230 block with no core shift, you got the strongest factory B wedge you can. There is no quality difference in mopar blocks. The older ones use a lower grade iron but can be thicker where you need it (again, sonic test to be sure) but later than '76 IIRC use a better grade iron, and are better manufactured, but are typically thinner over all. I prefer the later blocks myself, because the core shift is usually less, and the iron is better. I also owna good sonic testor...lol.