Ford did not start using production clearcoat paints on the Mustang until the 1990 model year, and still then not all of the production colors were C/C every year. Even some 1993 paints were still single stage.
1990 = 4 non-C/C (EH, EP, YC, YO), 7 C/C
1991 = 4 non-C/C (EM, EP, YC, YO), 8 C/C...