Many,if not all of the earlier ADs came with a 2 piece brake rod. Somewhere around "54 they went with a one piece red, probably to save a few pennies per truck.
The FAM has a some misleading information. Much of the information is '54 centric which leaves out a lot of accurate information about the earlier ADs.
The one piece rods do work just fine on earlier ADs.

1952 5-window - return to "as built" condition | 1950 3100 with a 235 and a T-5 transmission