James Best as Bart
The July 2015 issue of Classic Images Magazine has a long story about James Best by Joe Collura. In it, James is quoted as saying he turned down the role of Bart Maverick in the series because Warner Brothers wouldn't pay him $500 a week. He told them he could make $1500 as a guest star.
James Best might have made a very interesting Bart, but Jack Kelly was great in the role.