The factory Paint job was waaaay better than Maco or Earl Schieb!! I know of a 16 mile GNX that still has the factory run in the passenger door.
The day after I brought mine home from the dealer I block sanded and buffed the car. With Laquer that could be done in a day and it looked amazing. Just not as durable as the new stuff and was repainted 8 yers later.
They all came painted black from the factory (GN & Turbo Buicks). As a mater of fact ... there appears to be two coats of black. 1st was sprayed right up to the exhaust hanger mounting point. 2nd coat up to the the bend about 16' up. I worked at a GM dealership when these were new & still do now. The quality of the paint often wasn't the greatest. Often it showed up off the truck flaked. I seen the clean-up guys steel wool it off to make it look shinny for the showroom. the Gardner reproduction exhaust is 100% correct as well.