Clerical Whispers has an illustrated post on The Evolution Of The Popemobile. I expect that some would not wish this taught in schools since it is a theory rather than a fact - although the photos give some evidence of transitional popemobiles.
My own concern is, of course, the hermeneutic of continuity and I think we can discern this in papal transport. First look at this example from 1930, the Mercedes-Benz Nürburg 460, reckoned to the first real popemobile. Custom-built for Pope Pius XI, it has a central throne in the rear:
Now have a look at the Mercedes-Benz 300 SEL Laundaulet from 1966, just after the close of the second Vatican Council:
I think one can observe here a new expression of apostolic mobility without any essential break or rupture with the past.