63 Dodge Dart, now let me see;)

I had a similar issue in my 70. The aftermarket arms wouldn't slide in between the tabs. I grabbed a piece of all thread and outfitted two big washers and nuts and just kept turning the nuts against the washers and the tabs spread apart far enough to slide the uca just enough to hold th tabs and remove the all thread. Then just tap the uca in with a rubber mallet.