standard rb internalls are strong to around 300rwkw. that is as a weekender, most every day cars run around with 260-270 on standard internals as that is classified by all tuners as a safe tune on stock internals.
weak points are few and far between, your power goal is where weakness plays a part. main things to get your car there would be ecu, injectors, bigger turbo (not even a hi flow will get 260-270), fmic, 044 fuel pump, z32 afm, and any other supporting mods that may require replacing of stock parts to maintain reliability.
best way about going about this is to go and speak to a performance shop and explain what your plans are and what they recommened. your mechanic wont have sufficient knowledge nor the proper capabilities to set up and tune a 25orwkw car especially if they havent got a dyno.
thats my 2 cents