I installed a new/used transmission in my 1996 Audi A4 2.8 quattro auto.
Only after I installed the trans and torqued down the housing and converter bolt did I read in the Haynes manual:

"When installing the transaxle, make sure the marked stud on the torque converter engages with the marked hole on the driveplate".

I checked the converter of the original trans, but could find a mark.
I looked for a mark on the installed converter, but only found a welded on square (1/2 inch square) on the OD of the converter, and dent/hole in the flex plate.

Is it really required to match the converter and the flex plate?
How can I find the 'marked stud' and the 'marked hole'?