The blue truck is a 40 or 41. 38-39 has ribs at the beltline, as seen in the silver truck, and also has a larger back window. The 40-41 cab was used thru 47, but the 42-47 nose is wider and squarer. The rounded front fenders are the tell.

 

Likely the bumper on that truck was bought from this outfit
https://www.brizbumpers.com/