the rubber ring is the bearing support for the 66? nd later 120s. Your bearing support is the triangle thingy with 3 small posts that mate into 3 rubber grommets. As far as I remember the actual bearing is the same size, so you should be able to get the old style mount of your old shaft and onto this shaft. But as you only need the flange, why not just pull the uj apart and install the flange on your older shaft.
BTW the later style bearing support is a better design, I modified my 65 to accept it, using the bracket off a 68. But that was never going to be an all original car.