Do you mean a 93 w/slushbox vs other years with them, or the difference in general between auto and stick?
There was a thread a bit back that discussed the difference between manual and auto, but I don't recall ever reading about there being something special about a 93 auto. (which isn't saying much really as the topic doesn't come up all to often)
EDIT: Here is a thread that I dredged up sorta quicklike that has some info about the auto vs manual doughnut/giubo/front coupling that may be of some use.
I check the thread you linked, very informative.
The Drive Shaft Flex Joints for Auto is a 8-hole one, manual is 6-hole.
However, all the Alfa part suppliers only provide 6-hole one.
Since the auto transmission is ZF 3HP-22, same as BMW E21, so I check the BMW parts supplier, I do find a 8-hole one, but they point out the 8-hole one is for manual.