the wing windows do have different designs from earlier to later years, but it's only the actual glass and rubber seal that's different, the actual framework is the same, they do mount up exactly the same bwetween the years.
just did a swap on my dually from one i think is from a much earlier year, the glass is actually taller, than the one that was original to my '86.
installing the windshield doesn't really require sealant where the glass sits, maybe against the cab,,,but while installing the wndshield, use two people, it helps, drop it in the bottom of the rubber, use soapy water all the way around to create a sort of lubricant, and preferrably some sort of plastic, i use a flat blade screw driver, but you take a high chance of cracking the glass this way...
you'll see what you have to do with the rubber gasket, basically pulling the outer rubber out and around the glass all the way around until the glass drops right in.
then feed the zipper into it's home all the way around, that's a real fun part. again, using soapy water, it helps.
replaced several of them already, hell i have gotten to be so comfortable with this, i have removed windshields, just to tint up a visor strip on the top for an extremely clean, light leak free look.
