Couple of observations...yet another part number outside the ones already mentioned. To me, the back locks more like an 80 or 90s spincasted part due to the roughness. I have a 48603, close to the 485602 and that looks clean in the back, believed to be off a 71 car though, but original. Yours also has the beefy reinforced stem on the "P" which some say is) was OEM. So....still a bit of a mistery.