I grew up in that era and recall all the events very well. I never saw even one bit of credible evidence pointing to LBJ or anyone else besides from Oswald.
Johnson was a power hungry man who would do anything to be president. He realized that he was never going to be closer than VP as long as Kennedy was alive.
Robert A. Caro doesn't say this but while reading LBJ's bio’s this thought struck me like a bolt of lightning.
When faced with a "Who done it?" ask "Who benefits?".