Any biography of Reagan. He underwent a political conversion while head of the actors’union, when the communists were trying to take it over. That would be in the mid and late 40s. After his second marriage, he moved in new circles and entered Republican politics. His anti-communism was not just intellectual, it was visceral. His admiration of FDR was the appreciation of a great leader, not all his policies or all his deeds.
You're amending what you claimed in your last post. You said (and I paraphrase), "Reagan was a New Deal Democrat who admired FDR throughout his life."
It's hard to imagine Reagan ever being in foursquare agreement with the New Deal, or with admiring FDR to the end of his life. That runs counter to everything we know about the man. If you can't cite a source for your claim, I'm going to consider it your opinion only.