I fit a newer Dakota carrier in my 1974/8.25 case with just a bearing change. I thought just line you at one point when nothing seemed to be working or coming together.
But there are so many smart ( a lot smarter than me) folks here so it will come together in sure of it
So if you have ) if not get one)a better pic of the posi unit sitting in the case without the caps on so we can get a better look/idea on what you got going on in there.