Here is a picture of the upper inner for the R3.
I converted my 1963 Lark convertible a number of years ago to the 1952 upper a-arms and they work great.... and help it corner much better.... less roll....
You could also use upper a-arms from 1951, but they physically look different, and I think the steel bushings are a little smaller too....
If you find and use Delrin bushings, the advantage is that you can keep your current a-arms...., But Delrin????..