Reagan didn't survive the primary, which means that Ron Reagan would have had to be a Republican to be able to vote for his father.
Do you think Ron Reagan was a Republican in 1976?
If he wanted to support his father, he would have voted in the primary. As a Republican if such was required. However, is CA a state where you have to be registered as a Republican or RAT in order to vote in a particular primary?
Sure he did, he just didn't win enough delegates at the convention. He lost by a razor-thin 1,070 to Ford's 1,187.