When you say "even more", do you mean they're popular with the far-right IOTL? I honestly can't think of many Kennedy assassination theories that ARE right-wing in their viewpoint. Most of the ones I know are left-wing in a vague sort of way(eg. Kennedy was killed by the CIA in order to keep troops in Vietnam), or at most, right-wing but in a manner that we would now call anti-globalist(eg. Kennedy was killed by the Illuminati), which wasn't at that time really the standard conservative viewpoint, and actually transfers quite easily to the weirder sections of the left.
(Interestingly, the theory that he was killed by the Soviets or other Communists never really took off, even on the right.)
But I agree, if the primary suspect was a klansman, the lost-causers would be embracing every conspiracy-theory on offer to blame someone else. If Johnson turns out to be as progressive on civil-rights as he was IOTL, the popular theory would probably be that Kennedy was holding back on integration, so the Jews and LBJ had him killed in order to force mongrelization on America, and framed an innocent "white patriot" for the crime.