There is no diference between the EBXR6 and the standard 6 cly auto acording to the workshop manuals, just perhaps the diff ratio's.
The V8's however are diferent in that year but are the same in both the XR8 and standard as well. ( If you know what I mean)
I was told (yep, by a friend of a friend:s2: ) that the V8 box is a "heavy duty" version - something to do with materials of some parts inside - and that XR6's are fitted with V8 spec boxes (with 6cyl converters, input shafts etc.).