It's completely up to you. Personally, I don't care for plain black sidewalls unless it's a low profile tire. A stock restoration with dog dishes and whitewalls looks good. I've got a picture somewhere of a black Cuda with dog dishes and whitewalls....I like the look. I assume you're talking about the car in your signature. If you've got wider wheels and bigger tires then stock, I'd probably just run the black walls out. If it were mine, I would have gotten reproduction Polyglass tires in a RWL.
Have the blackwall out on one side and the whitewall out on the other. It will cost a little more to have the others switched back but you will be able to see what you like best.