Question regarding Windsor Ontario built cars (70 Swinger)

I was wondering what the underside was sealed with from the factory? Mine appears to be black (the same stuff the body was submerged in half way up) I have seen one other 1970 Swinger (Windsor built) done in the grayish blue sealer pictured below, but I'm unsure if that's right? Did they dip the cars and then paint them grey underneath with sealer afterwords? My roof had the Original paint on it and it was done in red oxide primer over the bare metal, then a bright green sealer and then the Hemi Orange.. It appears to have no grey sealer anywhere??

I am recreating the factory overspray look under my car and want to know which is the right look. This is a sept 1969 built 1970 Swinger 340




This is under the factory undercoat.


Here is a car that was restored (Windsor built 1970 Swinger 340)