This background is very much appreciated. Can you share which OEM your company supports?
In any case, hearing that you machine the cranks to your own specs goes a long way. Clearly BPE is taking ownership over the performance and functionality of this part of the engine. That says a lot.
No doubt, cast cranks are vastly better than they were in the 1970s...but this makes me curious. I have a modern Ford in my garage with a V8 engine (that makes less power than a 408 stroker) and Ford, not known for being particularly "generous" saw fit to include a forged crank shaft in the Coyote. This particular engine has a higher rev limit than the 408 but also a shorter stroke length (presumably similar piston speeds...too lazy to do the math :) ). It also has sophisticated fuel management which undoubtedly reduces the punishment taken by the rotating assembly. So if it's just old wives tales that say modern cast cranks aren't up to the task for a street performance engine, why did Ford go this route? And yes, Chevrolet uses a forged crank in the current gen LT1, Dodge uses a forged crank in the 6.4L/392 motor as well.
The question isn't specifically directed at Johnny Mac...