I understand your concern and your interest in preventive maintenance. If it was me, I'd replace everything I could while doing the project. Then, there's the old adage "if it ain't broke, don't fix it". Not sure what to suggest to you. If the car has a lot of mileage, I sure would replace what I could in an effort to stem off any future problems. If low mileage, save some money and go for broke!

Jim