Help.. with throwout bearing question

[Pflugerman]

I have a 69 c10 inline-6 250 4.1 w/three on the tree. Had what appeared to be a throw-out bearing (clutch thrust bearing) issue. Pulled the clutch and ready to replace the bearing. O'Reily's ordered one in yet it is a self aligning bearing vs thrust. Why two types of bearings for a c10 inline-6 250 4.1 w/three on the tree? Are they interchangeable? Which is recommended? Non of the auto parts people in any of the stores have a clue. Not a clue!

Your help is appreciated.