When I last worked on model minerals the only decent model was the Airfix, so I have a lot of them.
Modified as follows.
Top rail extended over door and flat smoothed.
Metal bearings added (but those horrible wheels still fitted!).
Either
Tie bar added, one brake reversed, 2 vac cylinders added, labeled as MXV.
or
Clasp brake gear, 2 vac cylinders, labeled as MCV.
I am happy with them.