[mickmate]

Hi Mark as Bobs pic from the handbook shows it's for the bearing retainer plate. Note the bearing style shown in the drawing. If the bearings used are tapered roller instead they can be shimmed between them to adjust. The front uprights are the same from 427 to 289 except the height is different. The 427 is taller to the upper ball joint, the 289 is shorter and has the leaf spring trunnion as you said. Do you have those yet?