I'm a new member so I'll summarize what I'm doing.

I purchased an all original '56 Chevy longbed (3200) pickup a few years ago and I've been working on making it road worthy and safe. Along the way, as I'm changing/upgrading, it's becoming a resto-rod.
The body is all original and about 90% perfect with a touch of rust in a few lower body panels.

I noticed that the seal, where the roof meets the drip rails, is almost gone. I remember seeing this on other classic cars and I thought it remained soft to the touch, like a putty. Is there a particular product for this? I don't want to use silicone because it's impossible to remove, come painting time. Maybe some kind of chalk?

Thanks in advance and I'm looking forward to helping others from my car building experience.