[vectorit]

No one is reproducing the masonite style that GM originally used.
I am making mine right now out of a material that is used in mobile home showers, kind of a melamine paneling but it's thin enough to bend for the headliner.
I tried using the white backed masonite from Home Depot, and it turned out to be too rigid to easily manipulate into the slots to hold up the panel. Was very frustrating, and I just trashed it all and went to the much thinner stuff. So far it looks to be working prett well.
I think there are others on the forum that have done it, so maybe they can provide a picture? I saw a burb at a truck show that did this, and it was very nice.

You are lucky that you have at least the rear piece to make a template out of, since that's half the battle right there is getting it cut to fit right.
Care not to break that chrome plastic that snapps onto the bows, since those aren't being reproduced yet either.