Any of the parts vendors sell the new reproduction ball bearing water pumps that don't leak.
Often the water necks are severely corroded because some dirt farmer ran straight water in the car and drained it every night in the winter time. You can sometimes get them sealed by installing the hoses with a smear of silicone RTV. Or you can buy new reproduction necks pretty cheap.
http://www.snydersantiqueauto.com/1928
1912 Model T Ford touring Salmon (ugh!)
1913 Model T Ford Touring original Black paint
1915 Model T Ford Roadster Black
1915 Model T Ford touring Black of course!
1967 Cougar GT 390 Cardinal Red / Black
1968 Cougar GTE 427 Augusta Green / Saddle
http://www.supermotors.net/vehicles/registry/15029/50071-2