Big Block Hp Capability

We're talking naturally aspirated or blown - not turbos and sorry for the wordiness...
The biggest problems I know of are the bores and the main webbing. The bores are not cast well (same as small blocks - core shift) and the bore centers are too close. When you're talking about heads that flow enough to make these power levels you begin to have issues because you can't fit enough intake valve in them. Also if the bore walls are inconsistent the ring seal can begin to go away and ring seal is huge if youwant to make these power levels. Some of that can be fixed with filling, but that doesn't work well if you need to drive the car (idle time, etc) because you can't fill up where the ring seal is most crutial unless it's a race only deal.
The main webbing, even in the early '71 "230" 400 blocks is not really good for these power levels. You can girdle them, and use better caps, and cross bolt - and the bottom will still eventually fall apart and cracks will appear in the main saddles. This is why I am against girdles and billet steel caps on big blocks. All they do is transmit the harmonics to the block better. The best way to keep a block alive is accept that at some performance level you need a better one. I would rather have a customer spend $5K on a completely machined KB aluminum block that will survive anything we can toss at it than spend $3500+ on a factory block, getting completely tested and machined, fit with a girdle, modified oiling, and lifter bore bushings. That $1500 difference pays for big weight reduction, safety, expandability, reliability, and rebuildability. If the engine buget is $16-18K we're talking about 9% to upgrade the block to "never need another one".
In terms of carnage -
Block #1 - 440: my ported 915s, MP .528, KB hypers, LY rods. It ran 11.60s in a B body with 4.10s and he drove it to the track (1.5hrs on the highway) and it had over 500 logbook passes down the track. The crank let go in the burnout box at 3500rpm and it scattered. The webbing had cracks that were ovisouly older (carbon/oil residue in them)
that had opened up and it blew.
Block #2 - 70's 440: had been run with the MP 509 cam and not much else but bolt ons. Made about 430hp. Lived that way for years of street abuse and never showed signs of problems. Upon disassembly for rebuild and stroking - the saddles had cracks in them and the caps were walking around.
Block #3 - Another friend - call him more of a mentor really - he had an 875hp RB 496 wedge explode on it's first pass after being flogged on the dyno. It took the right front tire off and put the car into the wall. This is not typical but when you're responsible for building something this potent I ask myself is the risk worth it? Again - these are not 12 second cars. Someone can be killed by a decision of going cheap and I take that seriously.