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.