OK, it sounds as though the end bonded rubber seal from Steele is the direction to go as far as a replacement part is concerned. If that doesn't work 100% in the end I like the suggestion made earlier about bonding an extra layer of sealing material onto the circumferential gasket. Shouldn't have to, but we'll see.
Now the remaining issue to resolve is to clean out those "drain holes" that are in the corner of the windshield frame opening on the cab. I was just out in the garage looking at those holes/tubes and sure enough their plugged! It'll be easy to unplug them. I can see from inside the little tubes on the inside of the truck up and behind the dash board. Their about 2 inches long and look to be no more than 1/8 inch in diameter. Problem there is no tubing connected to them to drain the water from out of the cab!

Does anyone know to where would you run new tubing from these drains to exit the cab? Is there an opening in the firewall somewhere? Has anyone ever seen an
illustration showing these two drains and how rubber tubing would be routed from them out of the cab?

I would think that by getting these little drains to function again that it might help solve everyones leak problems providing your actual windshield seal functions as it was designed to. There must be a way to conquer this problem!
