I decided to use some of the Malibu roof edge that extends past the rear of the S10 cab to make the cab look a bit more like a business coupe. I used a piece of cardboard to determine how much of an extension looked right. This is what I decided to use.
One month later... I finally got the windshield frame shaped and tacked. I included a couple of braces to hold the top and bottom pieces apart. Placed at the front of the cab, I finally can get an idea of how the windshield will match up with the Malibu windows. I am pleased with the look from the front as I think the angle of the edge of the windshield matches well with the angle of the window.
The side view is another matter. The A pillar will probably have more of an hourglass shape than I had envisioned unless I move the lower edge of the windshield deeper into the cowl.
Finally finished working out the shape of the windshield frame with the shrinker/stretcher tonight. I've wrapped the windshield in heavy paper to keep it from getting scratched during the frame assembly. Thanks to JMSTOY's (Zak's) tutorial on cutting glass with a roto bit and the effect of the heat generated by the tool, I now know not to attempt to weld the frame while it's supported by the glass.
I picked up this 58 Chevy Delray roof off of Craigslist for $100. It will be just barely wide enough, but I guess it's better to use a roof someone has already removed than to butcher an old car that has a roof intact. I wasn't searching for this model, but I think I'll use the back of the roof as the front of the S10 roof. The downward curve will work well with the curve of the Malibu door edge. Maybe I'll leave it with a little overhang over the windshield as a "fixed" visor.