The 14131 and the 14158 Both Come in Various Styles, and Will Fit in Place of Each Other. The Difference is the Cooling Direction of the Fan. The 14131 and 14158 Can Be Interchanged, as Long as the Correct Fan is Used for the Application. 290-104 Has the Plug at 3:00 (Earliest Version). 290-104A Has the Plug at 10:00, and Uses Earlier Stator and Rectifier Combinations. 290-104B Has the Plug at 10:00, Uses Later Version Stator and Rectifier Combinations, and (Most) Has a "Step" Cutout on the Top of the Plug.