Actual evidence is what I am interested in. Neither of them stated that they had done it or even been involved, merely a belief that it had been done and the statements are widely disputed. The second paragraph is about plots in Cuba. Your third is what a person unconnected to the murder believes. The fourth leaves the case against the mob entirely.
In terms of evidence, I'd say not even enough for an indictment.
What are you talking about?
To partially quote one legal definition of conspiracy:
Therefore, the very act of an agreement with criminal intent (along with an overt act, where required) is considered sufficiently dangerous to warrant charging conspiracy as an offense separate from the intended crime.
Carlos Marcello admits that he had him killed and wished he did it hmself, meaning he conspired with others. Marcello was in prison at the time. He died when the document was declassified and uncovered. So you can't have an indictment. John Gotti was indicted on wiretaps, so that informant's memo against Marcello would've have been sufficient evidence under normal circumstances.
Santos Trafficante confessed on his death bed (or when he was critically ill) to his lawyer. He's no longer around and his lawyer would not have indicted him. He only revealed the confession after his client's death so no solicitor-client privilege applies.
G. Robert Blakey is a law professor and he concluded that there was a conspiracy by the mob to kill the President based on the circumstantial evidence he examined, even though he didn't indict anyone.
You do not need to know the shooters or indict them to conclude that there was a conspiracy. All that's required is that there is proof, either direct or circumstantial evidence of a criminal agreement, as is sufficient under the law, to conclude that a conspiracy exists or existed.
For me, the most basic evidence that a conspiracy existed, and one doesn't even need to know who the parties are, is the Zapruder Film. An analysis of that can easily demonstrate that there was more than one shooter, whether or not Oswald was part of it.
Those who are pro-Warren Commission (like you?) will ignore or discount direct or circumstantial evidence that proves or suggests conspiracy, as well as contradictory statements in the Warren Commission Report itself. You need to see a smoking gun but even lone-nutters ignore the statements by witnesses that they smelled smoke or gunpowder around the grassy knoll, or that there was a puff of smoke around there too.