Sometimes a alignment issue can be very subtle. There was a Technical Service Bulletin published by Ford. TSB 93-25-3. There was an alignment issue caused by the A/C compressor mounting bosses being unequal.
I agree with the other responce. I would also look at the tensioner. Make sure it has plenty of tension and that there is not an alignment issue there either.
There are also belt wear marks on the tensioner. Sometimes when purchasing non factory belts the belt length may not be perfect and the tensioner may be bottoming out.
The other thing to look at is the depth of the power steering pulley. If it has ever been serviced/ changed someone may have pressed the pulley on too deep etc.