The only thing stopping you from going faster is the false limits you put on an oe block. Aftermarket blocks do not insure an engine will not fail.... it just makes an engine more tolerable to tuning mistakes.
Not saying everyone is capable of keeping an engine alive, but as long as there are those that can, shows it can be done. There definitely is some risk/ reward in trying.

"use it 'till it breaks, replace as needed"