Tim,
Here a link to one thread about this. (search by windshield+wedge)
http://www.sunbeamalpine.org/forum/showthread.php?t=10482&highlight=wedge+windshield
The last time I saw any in person was 30+ years ago, but I think they're about 1/2 inch wide, maybe 2.5" long, with two 1/4" holes about 1.75" apart. I cannot recall if they're steel, aluminum, or rubber-coated unobtanium.
Note that alternate methods are stacked washers, and an adjustable nut affair from SS.
Like folks said in the thread above, they go at the outside mounting bolts for the windshield frame, to even things up with respect to body variations. If the shape of your car necessitates their use, and they're not used, I could see that tightening the windshield frame down (to slightly compress the gasket, for example) at the ends could lead to undue stresses in the glass, causing it to crack at the high point of its support. (This may not happen until road flexing comes into play.)
If you check the fit between the door "wings" and the frame, from top to bottom, is it uniform and tight? Or is it wide at the bottom and tight at the top? I suppose it's possible that others in the past have adjusted the door wing frame, and subsequently the window fit and the soft top fit to match a windshield that is raked too far back, so this gap investigation should not be viewed as the final word on the subject.
I'm getting ready to do a soft top/hard top/tonneau/windows/doors adjustment project myself, and I'd be interested in knowing what the "right" angle is between, say, the interior door sill and the windshield frame. Knowing what it was supposed to be would help align all the adjustable bits aft of that point.
Good luck, and keep us posted with how things are going.
Ken