In the
1949 Chevrolet Truck Engineering Features pamphlet, the below information is listed detailing the purpose of the radiator support cross bracing improvement introduced for the 3100 trucks that year.
Basically boils down to a need was identified in earlier models that caused potential radiator stress and failures, so the radiator support was upgraded to change from a single to double lower mount point and adding cross braces to strengthen the unit and prevent potential damage to the radiator.
I'll second Otto's suggestion to put them back on.
