I have found some anecdotal references to DB being the primary supplier of half-tracks, trucks and staff cars using a google search, but no reference to actual archives to check.

There is an intersting post-war reference to MErcedes and Nazi's, namely the employment of Adolf Eichmann (a high ranking officer who carried out the holocaust) after the war in Argentina, where he worked as an technician at a Mercedes factory (from "The House on Garabaldi st."); Eichmann used an alias of course, but it is unknown whether MB Argentina was aware of his identity, given their pro-fascist disposition at that time.