So, it's simply too easy to say that there was no conspiracy because somebody would have come forward after all this time.
I was referring to a particular kind of conspiracy in which all the evidence against Oswald have been falsified ie. that Oswald was not involved.
I was not referring to a possibility that Oswald conspired with someone to assassinate JFK. That is still a possibility that the available evidence does not completely eliminate, although it appears to be very unlikely given the evidence that we do have. Marina certainly thought it was unlikely based her knowledge of his behaviour and character.
A conspiracy to falsify evidence not only of the assassination itself and all of the evidence linking him to the rifle and to the SN but also the evidence linking him to the murder of Officer Tippit and the attempted murder of General Walker is a totally different matter. That is an enormous amount of evidence that would have to have involved hundreds of officials who were duty bound not to participate in falsification of evidence.
So, either you accept the evidence as being genuine and subject only to unintentional random errors or inaccuracies, in which case Oswald is still guilty (but may have conspired with someone) OR you must accept a huge multi-level organized conspiracy involving hundreds of officials, none of whom have come forward with evidence of such a conspiracy in 60 years.