any thing past 260 gring in duration .. your springs will then suffer
i have a rb30det i used some (performance springs ) they are suited to 11.5mm lift ... and i have no problems with hks 264 with the custom 9.5-9.3 mm lift.
std preped rds like balanced and shot peened resized etc .. all help longjeverty.
i have 2530det using std preped rds making 330+rwkw..... boostworks have made over 471rwkw on std rods so
they are strong for they application in your na build