Don’t be silly.
You point out 1988 in a “time changes things” manner. You’re right. There is a significant difference between Reagan as a democrat prior to 1962 and Perry as a democrat until 1989.
If Perry was a democrat until 1989, failing to convert during Ronaldus Magnus’s two terms, then he’s utterly hopeless.
I am more interested in what Perry has done since he became a Republican, rather than before he changed. It is silly to say that because he didn't become a Republican before 1989 that ipso facto, he can't be a conservative.
And to further the analogy, Reagan changed from the Dem party in 1961, and ran for president in 1976, 14 years later. Perry, if he ran, will have been a Republican for 23 years before running for president. So if you take that as a metric, Perry has a longer and more stable record as a Republican then Reagan did when he first ran for president.