how much can it handle?
no nitrus and no supercharger/turbocharger...
if alot of bolt on mods were done.. (no price is too high kinda thing.. ) would the bottom end fall apart? (oh, and not reving the **** out of it..)

the question is pretty much, how much can a stock bottom end take in an LB9.

 

Never pushed an LB9 that hard but given it's low stock output I would think that an extra 100-125 HP would be no problem at all. It's still got a cast crank and pistons so like you said- don't rev the snot out of it and don't expect the pistons to last long under detonation conditions. But otherwise you would have to build a ton of torque before you started breaking cranks or bending rods.

 

The stock bottom end will handle anything that a N/ATPI will ever produce, given the RPM limits and flow restraints that TPI imposes. There's basically no way to exceed the bottom end's capacity as long as you stick with TPI no matter what you bolt on to it.