Cargo body with winch, banjo axles. 83xxx SN puts it about mid 42 production. The SN only conveys axles type, body (cargo, tipper, fuel, water etc) and if it has a winch.
You really want to ask about what parts are specific to the mid 42 models. On cckw.org there is a PDF by sinderlin (I think I spelled that wrong) which will give a basic overview of the larger parts that should be on.
I gave you a preliminary list (and was flamed for it) so I will not repost it.
One word of caution I will post openly is that if you do not have original data plates realize that NONE of the repro's available are correct. And no data plate for a production truck was in brass.
You will also need the early TM-10s for parts/maint. The TM-10 maint manuals are easy to find.. e-bay has plenty of copies available. The later SNLs cover open and closed cabs, but they are 44-45 pub dates and the open cab stopped production in early late 42 and were completely over with in early 43.