[Buick455]

For simplicity sake we will assume the stock cross member does not have holes like that of my 87 3/4 ton. Comparing the stock cross member made from cold rolled steel with and Sy of 35 Ksi and a piece of 2" OD 1/8" wall tubing with an Sy of 75 Ksi the stock cross member is stronger in that it will resist bending in the vertical direction which is primarily how this member is stressed. Combine this with how the round tubing is joined to the members it is a substandard design compared to the original. This is assuming the tubing OD is 2" which is hard to tell from the photo. If the tubing is 2.5" OD with 1/8" wall and if the ends were attached to the frame with gussets (transitioned from the tubing OD to the frame height) this would be a superior design to the original.