I found this one on the Rock Auto website, listed under 1989 F-250 w/460 EFI, the description says V-belt, but it is actually a serpentine belt.
GATES Part # K060675 More Info {#25060675, 2571715, 4060675} Micro-V AT Premium OE V-Ribbed Belt; K06-13/16" x 68" One of our most popular parts
Fan, Air Conditioning and Power Steering
Fan & Power Steering Belt; w/POWER STEERING Except AIR CONDITIONED
Air Conditioning, Fan & Power Steering Belt; AIR CONDITIONED and w/POWER STEERING
Fan and Power Steering; w/o A.C.