Changed out main door rubber seal
with part from Out-of-Doors Mart. First removed old, cracked rubber seal with razor blade, steel wire brush and finally a nylon bristle brush.
With the door open against the trailer, I started on the bottom trailing edge of the door and worked my way up and over without stretching the material at all. The bottom is sealed with a cut piece once you've done the upper part of the door in a continuous run. Note that the old seal on the 1974 Ambassador was under the hinges - this is not the case with the new seal.
Will post photos.