Steve, I bought a NOS set, L&R with part#'s, of UCAs with the welded angle like yours from a mopar guy a few years ago. He claimed they are for Big Block cars. I explained to him that I had never seen them before but he had a BB in his yard long ago with these UCAs. So that put me on a search and asked a couple of SUPPOSED A-body experts. These 2 guys NEVER saw them before either.
I checked my 5 BB cars and only 1 car has this type on the left side!!
That is a factory part so don't cut the angle off! Now I see one of these on your 340 car and adds to the whole confusion of what the heck they are!!!!!!!!!!