I have a couple copies of the re-issued AMT Chevy Van kits, and I intend to build ambulances out of them. My only problem is how to do the raised roof. I searched around and saw a couple of people did resin aftermarket roofs for this van, but I don't think anybody sells those anymore, so I was wondering how I could do this on my own. I imagine one would have to use styrene sheets such as Plastruct, but I'm open to any and all tips.