vibration problem

Funny thing about this vibration thing. I had TCI tell me that early 318's are pre balanced and don't reqire a balaced torque converter (with a weight welded to the side), but then couldn't expain to me when i asked "Then why did you sell me a torque converter with a weigh welded to it?" I have a 318 & 904 from a 1973 Satelite installed in my 1966 Barracuda. The 904 and the torque converter were sold to me by TCI as a set to match up to a 1973 motor. The converter vibrated like crazy and took out seals and bearings in the motor and tranny. TCI says they are not responsible...whatever. Any one here know if the converter should be weighted or not?