If you have the 2x3.5" retainer plate than it must be a big-bearing, correct? Thanks.
The only thing i found in my search shows 66-77 broncos, but i guess they are still the same for my 81 F150 axle.

there are at least 2 different large bearing ends

3.5x2.375 and 3.5625x2.0

the trucks usually had 1/2" bolts with the 3.5x2.375