Your asking the wrong question,
As Safechav has stated, different engines on same boost = different power.


You would of been better to ask how much bhp, lbft would a std gearbox last, using std size road tyres.


But then its still not a known amount, as some people kill gearbox's regularly on 160bhp/lbft.

Where as i haven't ever broke a RST box, and i have done 40k miles in my xr2 turbo running between 180-200 bhp, with upto 230 lbft.
inc lots of hard trackdays on slicks, and 100's of sprints.
But my xr2 is using smaller tyres (195/45/15) and wiegh's 1040kg's with me in it as road trim, 985kg's as trackday trim.
And my cars are used alot harder on a regular basis then most people would dream of.