I figured out where the water is getting into my 1979 Pontiac Catalina the other day by going through the car wash. Unfortunately for me, it's the driver's door seal and the water was quite a surprise. Haha. They don't pre-make weather stripping for this car that I've found. How much of a pain is it to use a generic roll of weather stripping to re-seal a door?
AutoZone has it - Metro - LM18-L-R - $82.99 for a set, both doors. I found at least 5 places that have these door seals - also - Classic Industries.
It's not that bad, especially if you have done it before.
You just want to make certain you have everything pressed on firmly, that it is in the weatherstripping track, that you clean away all the old adhesive before adding a new, quality adhesive, and basically take your time.