like your plan if feels well thought out. Any idea if a newer 99+ truck track width is the same as the 67-72's. If so an extended cab long bed would be just about right for what I am thinking
3/4ton frame with factory anti lock brakes, stronger frame modern componets and still enough of them in the wrecking yard without frame damage.
I was doing some work on a blazer project thias week end and after spending a few hours cutting open the rockers and getting everything ready for blasting before replacing all the damaged parts and I had an idea. The rocker boxes do a good job of adding stiffness to the convertables and is really only 1/8" brake shape sheetmetal. I was thinking this would do a real good job of adding plenty of stiffness to the large open span of a sucide 4dr
As for the head liner and doing a sculped design I think the easy way would be after the cab is all fabbed up if you can flip it over then use card boadr to rough out the shape that you want and cover it with foil then fiber glass it. It would only take 3 good layers to give you a real good base for covering. I would add a layer of 1/4" foam under the card board before glassing to give a little bit of space for dyda mat or insulation between the finished roof and headliner.
Well a few more days of comuting and I should have mine all built and painted
Kevin
LFD Inc.