Stock gsr/itr/ls/d16 injectors are 240cc.
LS rods will only work in a gsr if you have an ls crank.

Stock internals can handle 300 whp on pump gas without an issue, however the limits of the stock bottom end is going to be the cast piston ringlands.

Do not rate the limit of a setup by PSI....
Have your tuner advise you as to what your setup's limits are.