The head stay rotats if it is working correctly, the lower bearings in mine were bad, I pulled it apart and got the bearings from a company that moved to Irvine that sold Air Craft Bearings, They may no list them as a Mariner Part.
I have not hat to replace the upper bearing but the top of the rolling cable is splined and the eye for the halyard locks on it so when it rotates,
If the cable is the wrong size I have not tried to get the sweged on cable ends for one but that would be the pivit point for me.
I could have bought the drum & top bearing but both were frozen so as of yet I'm still waiting.
Also the top swedge makes the usable head stay shorter by about 10 " in my case. A new drifter came with my boat but it no longer fits.