C6 AOD Bolt on vs. New Units

[dandascott]

I have a C6 that has been sitting 30 years. I am debating getting the fluids changed in that (it was rebuilt when it was stored) and adding a Gear Vender AOD unit vs. buying a Lentech or Tremec transmission, AOD.

I have a 427 s.o. in a 67' Fairlane. Approximate HP is 550. Rear end ratio is 4.56 on a 9" rear end. I know the ratio is low, it is a long story but how I got there and I am hoping it is maneagable with the right torque converter.

Any opinions on which system might be the most robust ? most reliable ? offer lowest temperatures ?

Thanks in advance.