I have put the headliner in before and after the top material, and it makes no difference. Before installing the headliner and if your Model "A" has a dome light, make sure the power & ground wires are in place, and that the light works.
One other thing that occurred to me is that if you do the headliner first then any crap that may come loose while installing the top material will be trapped between the top and headliner.