Do the taillight extensions get seam sealed to the body before paint, or is there a gasket to use post paint?

On my original-paint cars I've seen overspray between the quarters & extensions, which tells me the extensions were at least loose if not separate.
Most all of mine had some kind of gasket, likely for anti-abrasion/chipping and/or sealing.
I've NEVER seen an original-paint car where the paint bridged the gap between quarter & extension (I'm 67 and clearly recall these cars new).
I'm referring to 68-70 B bodies, which I suppose you are judging by your sig.
I believe the same applies to A-bodies, etc.

I'm sure my '69 RR was seam sealed between the body and extensions. HOWEVER, in '83 I had the car repainted and when it came back there was no sealer present and the extensions had obviously been removed for painting. I don't know what they removed them but its possible there was no sealer there and they removed the extensions for proper paint coverage.