There are two styles of rear AA truck trans rear bearing retainer 4 speed . The most common is a pressed steel retainer which works with the muff coupling jack shaft . Later a bipartible U/J was used with a cast bearing retainer very similar to the 3 speed trans . With this setup you can change the clutch without Pulling the back axle back . It is easy to see which retainer they have ,
John in warm sunny Suffolk County England .