GM realized that they had a problem with cracking of the radiator supports due to flexing of the front end sheet metal.
Their fix was to switch from the single center mount, to dual mounts to the X member.
At the same time they added the extra X bracing rods across the uprights of the support to make sure that it would not flex.
My original 1950 panel van has a single mount support with no X bracing.
My original 51 truck has the dual mount support with the bracing so, I believe they made the improvements to the radiator support in 1951.
