1970 Dodge Dart - Got the passenger fender off, looks pretty good!

Today's fun was dealing with the passenger side drip rail. There was some rust in the bottom of the channel and some body filler where the seam goes. It looked like somebody put a bead of bondo in there with their finger at some point. I used a heat gun and metal pick to get the bondo out, and a plastic wheel, naval jelly and sandpaper to clean up the rust.

QUESTION: What should I do with the seam between the roof of the car and the outside lip of the drip rail? I pulled out the cracked and crusty bondo, but what is the right product to seal that area back up?

Thanks!