Not too familiar with what paint is available now, but back in the day with the original RM brand purple we added clear to the last coats of paint so it could be buffed and it lasted way better. They also used this color on imperials with 1/2 the metalic, deep plum, that looked really nice, and did not fall off and fade as bad. I am sure there is a single stage clear that will work, and I would use it or go base clear. Color you have looks good, I doubt they have the exact metal flakes anymore. Ppg and RM were a little off from each other in the 80s, but there is no doubt what color you have there is mopars purple.