RFK would definitely not have supported Reagan. He was more left-wing towards the end of his life than he was earlier in his life.
RFK would've been one of those Social Conservatives who would've joined the GOP in the 1970's had he lived. Much like the Huckabees did.
Conservatism as Reagan viewed it was like a three legged stool. The social conservatives (which RFK was one today's include Mike Pence,Michelle Bachamann ) economic conservatives (like Pierre DuPont IV, Jack Kemp and of current climate Ron Paul) and Defense Conservatives (like John Hostettler, Walter Jones). Neocons came to prominence in the 1990's in the GOP corrupting the stool.