Big John is right; the coolant hose dumps to the street.
I have put this type on three of the cars I have/had. I get them at Street Rod Shows; they work well and are easy to install. They will pass NHRA inspection too.
Found this on eat Summit:
KNS Accessories KA4203 KNS Accessories...
There was a guy in the Tehachapi, CA area who did excellent work repairing bumpers; he used to advertise at the Flings in Van Nuys. He moved to another State. Tried to find him on the internet; had no result. Perhaps you could do a search....
No, they are different. The 300 only had the lens fully across the rear; New Yorkers and others had twin sets.
You are correct about your front bumper; it's from a New Yorker or a Newport.
Here is a comparison of a '70 300 and a '70 Newport:
I saw a guy at Fall Fling this past weekend who was selling two of them. I encouraged him to log onto this site and contact you. He "doesn't do the internet."