Actually, i think the spreader bars have trunkated holes for the fasteners at the windshield. The mounting plate for the bar actually fits down into the windshield, not just sandwiches to it. I can take a few shots of my '88 AMC Wrangler (yes, it has AMC all over it) if you need to see how to do it. I have no idea about the Chrysler Wranglers, though.
You can see the spreader bar in this one. But to answer your question, yes, it can be done, but it would look like hammered $h..T. You'd have to drill through the windshield frame of the CJ, or INSERT IGNORE nut-serts, etc.