This is what Herb McCandless told me many years ago, if you build a maximum effort big block Chrysler and want it to hold together, either use aluminum rods or aluminum main caps, to help dampen the internal harmonics to keep it together. I have built several with both combinations, only one that broke was an aluminum rod engine, that by my mistake, I did not replace the rods when they were over time to do so.
I have never ran a girdle with aluminum main caps, seems like they would work against each other. Have built a couple with steel caps, and girdle, with aluminum rods. My experience with block failures that I have seen are in the number 2 main area, either the cap breaks, or the area between the main and cam bearing above the number 2 main cracks. I had one engine around 700HP level that I used the four bolt main conversion, water jackets had block filler, and a girdle, with aluminum rods, ran for several seasons. Started losing some ET, did a leak check and it was terrible, took the engine apart, the cylinders had barrel shaped and pushed so hard against the filler that it had hairline cracks between the freeze plugs on the outside of the block. That engine was bored .055 over, and I never had it sonic checked. But again it had around 600 runs on it. I look at it this way the original 440 block was engineered for what 400HP? When you bump an engine up to 750 HP or 800 HP , you are doubling the rated capacity of the block, the foundation of the entire engine. I finally learned and just purchased an aftermarket block, best decision I ever made. I know there was a shortage for a while, but I see several companies are now making and selling blocks again. With the machining cost of prepping a stock block, aftermarket caps, girdle, etc. then compare to the cost of the aftermarket block. Then realize that even if it holds together, when it comes time to freshen, will the block be a throw away?