President Reagan grew up in a time when immigrants assimilated and helped to build America. That influenced his thought process and the way he governed. Thirty years removed from Magnus, immigration has morphed into a weapon to gain political power. A better question might be what Reagan think and what would his policies be in 2019.
Immigration now and then are 2 totally separate ideas. And the numbers are overwhelming if you add together legal, refugees, and illegals. Not even close to the same thing.