Sulfuric acid and oleum are tricky substances to deal with because their corrosive properties change dramatically with velocity, concentration, impurities, and temperature. The details of design, fabrication, construction, inspection, and maintenance of sulfuric acid and oleum storage tanks and piping systems are contained in numerous documents and books based on many years of experience in the field. Two that I am familiar with are NACE standard SP0294 "Design, Fabrication, and Inspection of Storage Tank Systems for Concentrated Fresh and Process Sulfuric Acid and Oleum at Ambient Temperatures" and "Materials Selector for Hazardous Chemicals, Vol. 1: Sulfuric Acid, 2nd Edition" published by MTI. Obtaining copies of publications like these should answer most of your questions regarding storage tanks, piping, valves, etc. Regarding your last question, I am sorry but it is not our practice to recommend any specific vendors.