Does anyone really do this to their cooling system?
I first found the correct part number in my 1974 parts catalog (see photos), then bought a NOS one on e-Bay about a year and a half ago. I don't remember the name of the vendor. As an aside, I visited my favorite junkyard in western MN to find a spare radiator for my Duster at that same time. The slant six radiators are getting really hard to find, but I found one still with its factory original cap. The cap looked pretty worn, but I popped it on my Duster and it worked perfectly! Sorry, too much information - I know.