Mine had 19 spline WARN. 1960 GMC K1001. Dana 44. It does look like 20990 chrome and 9790 probably non chrome is the part number.
WARNING: Now-a-days....do not order anything unless from a well known company and get an email stating they are IN STOCK! IN HOUSE. READY TO SHIP. NO back order!!!!!!!!!!!!!!!!!!! NO drop ship from their vendor.