There's a lot to respond to in this post, so my mind may jump around a bit. First I'd like to say that these are just my opinions based on my life's experiences. Many may not agree, and many get pissed off, but I'm not trying to be a dick or start a fight.
The engine builders who post here regularly are brilliant guys. They have everything stacked against them and excel. They reinvent the wheel every day basically reengineering bad designs to give the Mopar community what they want. The hoops they jump through with oiling, cooling, valve train nonsense, ect is incredible. Trust me that Ford and Chevy guys don't deal with half that crap. They also have a niche market. Mopar guys who want to go fast have deep pockets and are used to catastrophic failures (it's just part of the game). The Mopar street crowd is a different breed too. They are building an engine that is going to hit the local car show 6 times during the summer. The owner will then post on here how his engine has lasted 20yrs with zero problems. As I stated these guys are brilliant. With brilliance usually comes a decent grasp on reality. I don't think any of these guys are going to tell you that these motors are meant to rack up miles.
Now here's where I'll probably piss people off. BBM's probably account for less than 1% of the engines I've dealt with, yet make up the VAST majority of catastrophic engine failures that I've seen. They had a pretty strong reputation for weak cranks. The only problem is it wasn't the cranks. It was the block gyrating like Axel Rose that would break the cranks, eat bearings, ect. As I stated in a recent post, I can even remember 200hp smog 440's blowing up. People can tell me I'm making it up or whatever. But just ask yourself, what's up with a whole market based around band-aids for Mopar blocks? Do you think Chevy and Ford guys even know what main girdles are? Aluminum main caps? Hell no. Most haven't even heard of hardblock. Aluminum rods were originally used to reduce rotating mass. In Mopars they use them as shock absorbers. To answer your question about HP limits...Well that depends on application. To rack up street miles my realistic HP limit would be around 400 with perfect machine work on a RB. Let's be honest again..most RB's never saw 100k before they hit the junkyard. For a burger joint car built by one of the guys on here, I'd follow their recommendations. For a race motor 650+HP, I would expect 1-2 seasons out of a fully prepped block.
