A 600 series comes with either an 8k or 9k steering axle. A 9k axle was used on the 950 series with a 671. You must keep in mind that the steering axle was not only designed to carry the weight of the engine but also part of the load. We usually put the 5th wheel about 18" in front of the drive axle which put about 3k load on the steering axle.
