Narrowing an 8 1/4" rear end, how is it done?

jcwren said
I'll continue to keep an eye out for a 8 1/4" from a 62' to 65'

Just so you know, there were no '62-'65 8.25s. I believe the reference was made regarding 8.75 differentials.
8.25s didn't come on the scene until early to mid'70s.