727 Tranny Leaks

Have a 727 behind a BluePrint 408 Crate Engine. In a '73 Dart Sport. Plenty of power etc. Of late the rear Trans Seal leaks and fluid leaks out where the speedometer cable goes in. On a 250 road trip at 70mph (turning about 2700 rpm), I can lose a quart of fluid. BTW it blew off one of the rubber hoses where tranny lines connect to radiator about two years ago. Replaced hose and used extra clamps and no further problems there. This Tranny has been rebuilt twice since I bought the in 2006. It has had seals replaced in the last 5 years. I hesitate to take it to Ammco as they don't have the best rep for Classic Cars. Any ideas or suggestions on what to try next?