Both prior posts make sense. I know a guy whose running an MS3 in a otherwise stock longblock with a 150-shot and is planning on a 200. If it weren't for his 10-bolt finally taking a dump (and causing the stock 4L60E to break) his bottom end would've been fine. He has it tuned really well though, so I'm sure that helps, but it's my understanding the crank and rods (not so much the rod bolts on early LS1s) are pretty stout and even the pistons will put up with some abuse.
"...What IS true: We anticipated that this would happen - we are never finished - and yes, Ford DOES deserve to win now and then. To think that GM can come out with a car to make ford throw in the towel is simply foolhardy..." - fbodfather