The fact that King was supposedly registered as a Republican does not mean in any way that he was a believer in the GOP philosophy of free enterprise, limited government, individual rights and intitiative, strong national defense, anti-communism, and so forth. He didn't support any of those things.
are you suggesting the conservatives were not Republicans when these changes were made?
Well, I don’t know about him supporting the Vietcong. I know he definitely wasn’t supporting American efforts in Vietnam, that much is true but I don’t recall him specifically endorsing the Vietcong from my research. Just because one doesn’t support America during that time doesn’t automatically make them VC supporters. Even one of the Politically Incorrect Guides, either the one about the 1960s or the Vietnam War, made it pretty clear that, while a significant minority among the anti-war groups, there were indeed people in the anti-war movement who also didn’t tolerate communism and did not support it.
As far as anti-communism and strong national defense, well, he did write a piece called “Can a Christian be a Communist” that eviscerated Communism by stating it was irreconcilable with Christian thought and was atheistic in nature, and I heard that he’s apparently a strong advocate for the second amendment. I’m also pretty sure based on Aleida Scott King that he’s also very much anti-abortion as well, which definitely is a conservative view (I’m pretty sure if he were 100% leftist, he’d be backing abortion and singing praises for it, and his niece would either parrot the same, or otherwise state her support for the repeal of Roe v. Wade is to go against her uncle, and I’m definitely certain he wouldn’t have written that essay denouncing Communism as a godless charlatan mockery of Christianity.).