Larry "Doc", Sal and Richard all being veteran Marines, they must know the Marine "Colonel Wilits" wearing a silver oak leaf rank insignia on his uniform should always be properly and fully addressed as "Lieutenant Colonel", instead shortened to just "Colonel".
While Sal and Mule are driving to and from the U-Haul store, they're supposed to be in central Delaware, near Dover Air Force Base, on the Delmarva Peninsula, which is one of the flattest places in the US. The highest point is less than 20 feet above sea level. In the film, they passed hills, houses on hills, and areas that looked much more like western Pennsylvania (shot in Pittsburg) than Delaware. Nothing worked, except for viewers who have never been in Delaware.
Colonel Wilits is wearing silver jump wings with a star above it. Only the army wears this badge, the Marines wear basic silver jump wings if they have fewer than 10 jumps or no combat jumps. Otherwise, they have gold wings.
In the funeral scene, Lance Corporal Washington is wearing his Marine Dress Blue uniform but his cover is not square, it is cocked to the right. Marines are always "squared away" and that includes their cover.