Toms cutlass

I've replaced several transmission gasket seals (speedo seals, fill tube, gear selector shaft, front & rear seals) and installed new cooler lines on my 350TH automatic. No more leaks, however I want complete peace of mind and need to replace the original seal on the detent kickdown cable. What is the exact size of the detent O-ring (couldn't find in existing threads)? Also, can I use the new-and-improved tophat type seal on the detent cable rather than the O-ring? I've read differing thoughts. Thanks in advance.