20-8790 is the Williams part number for a nyliner bearing used for 1/4 inch diameter shafts. (Bearing length .078 inch) That is what you need for A-16317.
Additionally, Williams used a suffix -1 through -9 for nyliner bearings with different lengths or for different shaft diameters. For example, 20-8790-1 is a nyliner bearing for a 3/16 inch shaft. 20-8790-2 is for a 5/16 inch shaft.