How much horsepower can a stock 2jz handle

From what I've seen and read 2jz engines can handle upwards of 800hp with stock internals.

If you have a JDM engine the turbos are ceramic and can safely handle about 17.4 psi (1.2 bar), but if you got the US version the steel turbo blades can go up to 20.3 psi (1.4 bar). The 1.2 bar pressure is known to make the engine develop around 400 hp, so this should be both safe and sufficient for this setup.

300-350 you'll be fine. Gte head-gasket and head studs for security and ur good.

Having a closed-deck design means that the cylinders themselves are much more stronger, and this gives the engine the ability to handle a high amount of power and will also last longer. This is why the 2JZ-GTE model was able to perform well with a high turbo boost pressure.