i always found using 1/2" drive tools for this job to be frightening because of the torque wind-up. any tool breakage, and that is easily possible with breaking torques well in excess of 300Nm, could lead to serious injury. i recommend 3/4" drive instead - virtually eliminates wind-up, and thus is much much safer.
i think it also worth mentioning that impact tools are a better solution. while they're not cheap, they do make the job a lot quicker and safer. there are a number of cordless divers available now with very high output torques, and they are, in my opinion, a great investment if you work on your own vehicle.
and high value applications go well beyond crank pulley bolts. e.g. rusted exhaust bolts. normally, they would be broken or need cutting off involving considerable expense, time and frustration. with an impact driver, they come right off.