3 years ago I purchsed a 112 year old home with a furnace system that has 4" supply ducts to all registers, including the one on the 2nd floor. These ducts are individually supplied direct from the furnace and not from a common supply duct. Yes, it is quite the mess in the basement. I understand that the ducts need to be upgraded as well as the organization of the ducts. Looking for a resource on the proper duct size and design orientation for the ducts.