I may be wrong but just from my memory, the motorplate spacer has a precision bore that fits over the snout on the crankshaft flange.
The flex plate also goes onto this precision snout.
The converter snout fits inside of the precision bore inside the flex plate. Nothing is changed with the converter to flex plate arrangement. As was said that is the beauty of using a spacer behind the flex plate. You can change the converter without it being custom made.
I have to unbolt my trans from the motor shortly so I will take some pics and check this.