Power Steering Belt

On a ‘74 Duster 225. What size are you guys running? I’ve tried 5 different sizes and nothing seems proper. I’ve got the federal pump and the adjustment screw is not featured on mine. Its as if its a fixed bracket. Am I missing something? Probably so! How do I get this thing on there? Any help is appreciated.

*I have the manual, but the instructions are showing/telling differently to what I have in front of me.