Try looking at the bearing and seal for the roller bearing rear. Maybe they fit. (?)
Does the old bearing have balls or rollers in it?
http://www.1968firebird.org/number/abw/abw32.jpg

Ask for 1971 cutlass with 10bolt for late 69 roller bearing axle parts. I think BR9 and 2146 or 48? (alternate seal 16735 0.4700 width or 16747 0.3750 width, NAPA listing)
Somebody here or on the list has pictures of a roller bearing rear axle. I can't remember where the seal was, if pictured.