Emm, interesting. The last dyno run was 465 ft lbs of torque.. Maybe i'm pushing it looking for more still.Gearboxes are rated by their torque handling capacity, not BHP. Given near to stock rear wheel and tyre sizes and none slick tyres, used as a track day toy, with NO racing starts off the line I had pretty good reliability from my stock R33 GTS-t gearbox with 360 ft lbs of torque through it. Nothing broke but it had the usual tired synchros after a few thousand miles.
internals are the same ,A GTST will strip thrid gear like a GTR is the car has enough grip ( ie running proper drag slicks) We rebuild the gearboxes with OS Giken internalsincluding larger input shaft,OS Giken strengthened centre plate seem to be able to run pretty good amounts of torque then , but as Chris says it is the shock of launching that will kill a gearbox thats why drag cars runs slipper clutches takes the initial load off of the gearbox.