It will be tough to tell without knowing the details of that swap . Giving you a boost / psi number at random can cause your car a lot of problems if such number is not supported by all the necessary components. What turbo does it have ? Single (what size ) or stock twins .. if stock twins .. usdm or jdm ? One is stronger than the other . What fuel pump does it have ? If I tell you a certain boost level and your fuel supply isn't enough , there goes your engine. What size of injectors ? without the right injectors providing the fuel will get you lean and damage the engine . What ECU ? What fuel ? What compression ? ....and so on ... let us know every detail of that swap .

But to answer the question "how strong are the stock 2jzGTE internals are (crank, rods , pistons) ? They can handle 700rwhp all day with the right supporting components and proper tune. Some have made +800,+900 and a little more than 1000rwhp but it will be on borrowed times. The ECU tune and failsafes play a very important role the higher HP you get. Most especially , it is the torque that will damage those stock rods , bending them or their weakest link being the rod bolts giving way. The use of the car will play a role on how long the setup lasts too. A 700rwhp car regularly used at the drag strip will not last as long as a 700rwhp car which is a daily driver that seldom is abused.

So boost number to get into a certain power level will be relative based on the components you have in the car. Two cars using let's say 17psi of boost wouldn't necessarily make same power level. So asking for a number can be asking for trouble for your car without giving more info.