Fender Sealing

Im doing the final fitting of the front fenders on my 66 Dart. When I finally put them together for the last time what material do you use between the body engine compartment flange and the fender flange to keep water / moisture from coming up into the engine compartment. I went to NAPA today and they had what I always called dumdum sealer. This is in a 25' roll, its about 1/8" thick and 1 7/8" wide. I was thinking this would be a much better seal then what I was originally going to use which was the topper sealer stick on foam. I'll add a pic or 2 tonight of the dumdum sealer and the fender flange.
Thanks Rod