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.
I've been fabricating a frame for the 55 Chevy windshield using 14 feet of 18 ga sheet metal bent to 90 degrees and a hand-operated shrinker/stretcher. I have discovered why the hand-operated versions are so much cheaper than the foot-operated ones - you have to do reps like a body builder to get anything done with the hand-operated version. This old fart has to go in and rest after about an hour of mashing on the thing. Anyhow, I've got six of the eight required pieces complete. Once the blister in my palm heals I'll have a go at the remaining two pieces.
The photo of the pieces laying flat does not do justice to the fit of the pieces in 3 dimensions, but they won't hang on the glass by themselves.
Marrying the Malibu passenger rear window frame to the driver's side S10 door went much faster (3 days). Now I have both frames mounted and have test-fit the glass with the weatherstripping and the power window motors. Both windows function properly with no scrapes or snags, although they don't go down as far as I'd like. Oh well. I have hung the doors back on the cab and checked the alignment of the tops. Luckily, they're dead-on level. Now I can start fitting the Malibu roof/door frames and fabricating the windshield frame.