The steering arm should be mounted to the steering spindle with the 2 balls facing the rear of the tractor. Is that the way you're trying to put it on?
A 38" fixed tread front axle with a B2840R casting number is for a BW starting at ser.# 201000 (mid '47). It might also be for a 50,520, or 530. A look at the parts catalog for your 530 would tell for sure.