Yeah, the MA61 spoiler will fit the back of the RA60 because the tailgates are identical just without the holes. The only problem that you may come across is either to put a hole in the rear window to support the wing which is on the MA61 or to leave it which may bow the spoiler a little bit...
Hope that helps. If you need help mounting the spoiler contact MaxDamage75. He has added it to his SA63 but did not put a hole in the window...