A while back, I was inquiring on this site about what I could use to go between the chrome piece that holds the roof rail weatherstripping on and the body. I didn't get an answer, but I did get a few guys saying that they too were looking for somthing for this. Well I found a product that works. It's actually made for this purpose. The stuff is made by Wurth and it's called sponge weatherstrip. It's 5/32" thick and 3/4" wide. It comes in 5/8 wide which would be better, but there was none in stock at the time so I just trimmed the 3/4" to 5/8". The part number is K08275 there is another number on the package (894.4852) but I'm not sure what it is. This stuff can be obtained from body shop supply places.
Hope this helps.
Jim