usually too late for a rebuild anyway. The center housing itself is a wear item that doesn't get replaced unless you get a new CHRA.
If your turbos are still working OK and just have high mileage and you have the engine out for some other reason rebuilding might be an option. This would give you a chance to clean and inspect the turbos. Gpopshop.com has good quality kits and have worked well for me. New CHRA still the best option. That or new bigger turbos.