"
Can you source this date please?"
Follow the link here,
http://www.ontheissues.org/donald_trump.htm#Tax_Reform
then the link, "10 full quotes on Tax Reform."
You'll see "Source: PBS News Hour "2016 Candidate Stands" series , Jun 16, 2015." That's where the quote or statement from Donald Trump should be. We should try to find a transcript or video, when time allows. Paraphrasing from PBS isn't good enough. We'll need to get it from Donald Trump in the form of a quote or video.
He's also 69. It's up to each person to decide whether or not he would have been likely to move from one end of politics to the other in later years.