The 2nd link above refers to the more updated modern "Fluid Torque Drive" torque converter.
It came about in 1951 on the Chrysler Hemi cars as an option. It is a true torque converter- not a fluid coupling as in the regular 1950 Chrysler. The fluid in FTD should be changed out as the factory manual states. In early 1951 this a huge 10-12 quart oil change. In 1952 the design was simplified and had a regular oil pan sump requiring less oil to change out and much easier to change the fluid.
The M-6 trans was still the same design but a different ratio gear set for the FTD. 10W oil in it as before to change out.
Bob
.