1. I would follow instructions in the 1955 Fisher Body Manual, secction 2 (
LINK). You won't be able to overlap. Per the manual, you create the butt joint at a specific place at bottom of door. You use adhesive only across bottom and a short distance up front and back. The rest of it, you just clip in. That will make it easier.
Here is my installation of weatherstrip on my Safari door, hardtop style, not sedan.
A friend that had a business restoring cars helped me. We installed a short section at a time with adhesive and taped it. then moved on to go all around the door. Per the instructions, you will not be using adhesive up the sides like we did.
2. I always check with CPR first, I've found prices are sometimes a little better than Ames, but occasionally a little higher. Prices for rubber bumpers will probably be close (also expensive).