413 blocks are not usually very thick although I have heard of some 413 blocks that were made from 426 cores. Not sure that is true or not. The typical 413 engine was just like any other Mopar engine cast in the day, that is, they usually suck. The Mopar casting plants had poor quality control so there is usually a fair amount of cores shift. One side of the cylinders will be great, the other side thin. Almost every Mopar block I've ever tested has core shift.
Mopar blocks aren't as bad as Ford blocks, but they aren't great. Best factory blocks are Chevy big blocks. I've never seen a standard bore Chevy big block that was too thin for performance use. Most Ford blocks are too thin for performance use while roughly 50% of all Mopar blocks are too thin.
Many early industrial 413 blocks are over .300" thick before boring which is why they are typically used for NHRA stock 426s. Some mid 60s 383 blocks I have and my 58 350 are well into the high .200"s and low .300"s. I don't think the 70s 413s are quite as consistently thick. The standard 413s are quite thin with the exception of the 1964 2205897 block which was also used for the 426 street wedge as well as a few Max Wedges.
