The (bad) TV series Shazam!, based on the DC Comics property of the same name, ran from 1974-1977. A few aspects of the series contain totally original material, from young Billy Batson having a mentor named, get this, Mentor, who drives him around in a caravan with the Shazam logo on the front of it. In the show, Billy frequently consults a glowing ball that gives him access to the gods and king that give his powers derive from. Were any of these elements later adapted for the comics? Did he ever gain an elderly sidekick named Mentor whose relationship to him is hopefully explained? Does he ever get a "Sha-van?"
Well, the loosely cited Wikipedia entry for Shazam (Tv Series) answers two of your questions.
For a brief time, Uncle Dudley became the role of Mentor in the comics.
The Mentor character, as played by Les Tremayne, was unique to the TV series and did not originate from the Shazam! comics. His background, and the origin of his relationship to Billy, were never explained.
In later issues of the 1970s Shazam! comics meant to tie-in with the TV show, Billy's Uncle Dudley grows a moustache, drives Billy around the country in an RV, and tells Billy that the Wizard Shazam chose him to be Billy's "mentor", essentially turning Dudley into the comic book version of Mentor. The Mentor character has not been used since[.]
The RV has occasionally been referenced later
[A]lthough Uncle Dudley is shown driving a similar RV in the 2010s animated series Justice League Action.