Many, many years ago, when I rebuilt the 389 in my 62 Bonneville, I drained the transmission but not the coupling. I swear it took 8 qts of Dextron II to fill it; don't know why I remember that number so well; I guess it could have been 7 but that's not what I recall. This was 73 and Dextron II was fairly new to the market at the time.
Besides the Bonneville, there was a 62 Cat 389 in our family. I drove both quite a bit. To me, the Super Hydramatic was clearly a superior trans to the Cat's Roto. The S-H 1-2 shift was damn near impossible to feel.
Sometimes I think about getting myself another 62 B body & reliving past glory by rebuilding the 389 the same way. If it turns out to be a Cat or GP, I will make the effort to convert to a S-H if at all possible.
