They make the TKO 500 and the TKO 600. Those are rated 500 ft-lb and 600 ft-lb of torque respectively. Since the 3550 went into factory cars that made over 300 ft-lb of torque, I would guess it is good to 400 ft-lb.
Torque is what breaks parts. The RPM is not as important, unless you are concerned with
oil temp. Cars spend little time a high hp, so torque is the important number.