Even for 50 yr old factory stuff, MOPAR rods were usually much better then the competitions rods. All that said, regardless of the brand name on them, rods were factory tested and rated for cycles, the number of times they could be stressed to the max before the material itself failed to return to its original dimension. I've run factory MOPAR rods in small and big blocks to over 7k with no issues. Now in the case of most small blocks the front of the block cracks at the oil passages to the main bearing bore before rod failure many times. But cracking here is not as noticed as a failed rod. Knowledged machinists can tell you a large portion of 340 blocks were taken out of service because of this issue but it works the same with any LA block, likely even others. The fact is when a rod fails it takes the block out with it so those cracks are not even searched for.
