Unless your seals have large cracks in them they can be renewed with a generous application of glycerin. You can usually pick this up at drug stores since its' main use today seems to be for skin care.

This is not a voodoo fix of my own. Mercedes would recommend this back then. So would Porsche. The great killer of this treatment was the invention in the early 70's of Armor-All which was easier to apply, easier to find, and easier to see quick results.

Don't be upset if it takes a lot. Dry seals will soak this stuff up but when you are finished the seals will again be pliable. And they should be watertight.