One thing's for sure, LBJ had far more to gain from JFK's death than anyone else. He was facing a possible prison sentence for corruption (I forget the specifics) so when the presidency fell into his lap, besides the obvious perks of being the most powerful man in the world, his legal problems were forgotten.
Here is what Roger Stone, former aide to Reagan and a confidant of Nixon, says about LBJ:
"I think the reason why he(LBJ)is the most logical murderer of John Kennedy is that in November of 1963 Lyndon Johnson was a man, who was looking into the abyss. He was tangled up in at least two of the major public corruption scandals of the day: the Bobby Baker scandal – Baker was Johnson's right-hand man, who was taking huge bribes on Johnson's behalf in the US Senate and then Billie Sol Estes scandal. Estes was a Texas wheeler dealer businessman who had got millions of dollars in Federal contracts thanks to Lyndon Johnson. Both of those investigations were coming to a head, both of them pointed to corruption by Johnson, corruption of Biblical proportions. And Johnson knew he was going to be dumped from the ticket and probably sent to prison. So, time was running out for Lyndon Johnson. He knew that Life magazine – a very prominent American magazine at the time – planned a major expose of his financial situation and his corruption. A week after the assassination and that the information for the Life magazine article had been sent to them by attorney general Robert Kennedy who very very much wanted Lyndon Johnson off the national ticket in 1964, so he, Lyndon Johnson is your most likely perpetrator.
I believe that Malcolm Wallace, who was a long-time associate and hitman for LBJ is the actual killer, I tie Johnson to at least eight murders in Texas prior to John F. Kennedy. These were murders to cover up corruption, they were murders to cover up voter fraud through theft of elections. Johnson had murder in his repertoire. In fact I would go so far as to say that Johnson could order a murder the way you and I would order a sandwich..."
Yeah, LBJ was a sweetheart.