making your own fiberglass headliner... anyone done it?

Use the outside of the cab to make a plug. That should give you the general shape and allow you to add or build up different areas.

 

I did a somewhat similar method on the headliner in my 4dr Dodge. A trip to the art supply store and an afternoon and I had this:



Quick deats: I striped the original headliner (which were a series of curved cardboard w foam that turned to complete crap over the years) and glued felt directly to the metal roof structure (giving the print something to bite into and softens edges):



Then I used ModPodge glue to adhere my desired print to the felt, layered the image, and finished it with a few coats of Shellac-type clear coat I brushed on. For the print, I cut out about a hundred vintage Men's interest comics and layered them on one-by-one.



It's been holding up well for 3+ years, aside from faded sun-exposed spots. And no one has on like it.