727 kickdown

Does anyone know if aftermarket kickdown/throttle pressure cables work? I have a 68 Dart that had a 904. It never shifted right. I then, for other reasons, went to a 727. I have the same problem. I have been told that the fulcrum lever that attaches to the bell housing is different from 727 and 904. Problem is, I dont know if I have parts from both trannies mixed. I adjusted the linkage correctly and it shifts late, I adjust it the other way and I get passing gear at 70mph. I see Summit has a cable kit, anyone out there tried it? Thanks
Author: Tazdevilish