When you say stock, do you mean stock as in, form the factory, or stock as in, stock rods and crank?
I run stock rods and a factory crank in my race motor and it regularly sees 8k rpm. I had a standard bore motor I cheap rebuilt (wasnt balanced, stock rod bolts, stock cast pistons,) and I shifted it at 6200 rpm.
Its all stock components, rebuilt by the previous owner, engine is at about 65k miles now (wow i sure drove it alot since i bought it) I dobut it was balanced well, but it runs good, no vibes at 5k at all. Thanks for all the responses, glad to know the bottom ends are fairly strong.