Don---I recently seen a magazine article that relates to what you are talking about, plus I have been engaged in ongoing talks with some convertible top manufacturers in British Columbia. In the magazine article that I seen, the windshield posts that bolt to the cowl were cast from brass and had a slot milled on the inside which was just wide enough to accept the windshield glass and some of the same kind of material that you use to seat a side glass in a roll up track mechanism. (I don't know what it is called). A slot was cut into the peice of sheet metal that spans across the top of the cowl below the glass, and a u shaped peice of sheet metal (the same width as the milled slots) was welded into it to accept the bottom of the windshield. A simple u shaped channel was formed to cap the open top side of the windshield, and after the windshield was slid down into the slot the top peice was attached to the top of the windshield posts with a countersunk head screw (one on each post). I really don't know what the windshield header on a model A looks like, but the convertible top people I have been talking to make tops for 32 Fords. The 32 Ford has a cylindrical stub which pivots at the top of the windshield post, so that no matter what angle the posts are at this stub can be rotated into the vertical, to engage holes in the aluminum header. This header sets down over the stubs, and a setscrew holds them in place. This aluminum header (which is actually part of the convertible top) has a soft rubber molding attached to its underside, so that when the header is setting in place on the vertical stubs, it rides tight against the front of the windshield to seal out the rain and wind. I hope this helps some.