What
The reason a Powerglide works well is because it does not have a low gear like a Turbo 400. The lack of gear multiplication makes the converter multiply torque better and results in a faster car most times.
Rear end gear ratio and tire diameter will make more difference than trans ratio.
1.80 works more times than not even on a small block if the proper converter is used.
Look at all the transmissions for sale on this site and you will see few lower than 1.80.