Not an uncommon problem. That small area of frame takes all the load from the steering at whatever pressure the pump and box provide, weight of the wheels, road impacts transferred through the steering linkage etc. Drive that washboard road at 50 and all those little impacts are hammering that frame rail. Flex metal enough it cracks, Chevy is not the only ones where this is an Issue. On older trucks with single wall frames the steering box would just shred a hole in the frame rail because the frame would crack from bolt hole to bolt hole. The brace triangulates the lower crossmember to the frame rails. It's there to stiffen it up.