The last thing I'd do is even consider reusing a 30+ year-old piece of rubber.

Mine leaks. It's leaked since about 1990, but in the last 2 years, it's really gone to hell RAPIDLY. It used to be soft, now it's all cracked and split. As are my door seals, trunk seal, rear window seal, etc... Just get a new one! You'll be glad you spent the money when it doesnt leak in a year.