George,
Will try to answer in order
1. I went down and placed the rear glass rubber in front. If glued in with each half "may" work. Without the frame you would need to add approx. 2" in glass as frame is approx 1" in width. I'm thinking you will still have to have/use some sort of divider to cover silicone. My opinion.....
2. Glass bought locally should be cheaper and no shipping cost. I have patterns if needed. Will need to locate...
3. Steele Rubber is one of the most popular but not cheap rubber companies, Very few negative comments
4. Local if available.....Again I have a pattern

The pictures of your truck looks great. You need to share here if you haven't. Have fun and good luck
Dan