However these 2000-2012 10-speed and 11-speed rear mechs have a different cinematic to the 1993-1999 8-speed and 9-speed rear mech.
Therefore they cannot be swapped. And I could not use a 31-tooth wrap Campagnolo 11-Speed rear mech with a 1999 Campagnolo Athena 9-speed ergo levers.
Well that was until the 9-speed Athena ergo lever got modified into a 10-speed ergo lever.
The internet is full of resources on how to carry out such upgrade from 9-speed (or even 8-speed) to 10-speed. It's not complex and with a bit of patience and curiosity anyone can do it.
Basically most parts are identical on all ergo levers from 1993 to 2008 and even more so with the BB System ergo levers from 1996. You will just need to replace a few parts of your original ergo levers with those collected from a 2000-2008 10-speed ergo levers.
There are a few variations actually based on your original ergo lever specs - with or without central ball bearings (BB System), with or without a third coil spring, etc.. But the key principles remain the same.
If you are interested in upgrading your 8 or 9-speed ergo levers to a 10-speed set-up, and would like to give it a go I would advise you first have a look at the following thread:
https://forums.thepaceline.net/showthread.php?t=250411
The parts that need to be replaced are all listed with their reference numbers.
You could also download and print the Campagnolo spare part catalogues from the relevant year for your 8-speed or 9-speed ergo levers as well as the 2008 catalogue for the parts to be collected. That will provide visual clarity on the internal mechanics and especially the parts that need replacing.
Campagnolo spare part catalogues are available on Campagnolo official website:
https://www.campagnolo.com/NL/en/Support/download
You could also have a look at the 2008 ergo disassembly tutorial:
But basically here is how it looks once everything is disassembled with the new 10-speed parts prior to reassembling.