I have the option to buy an st 3 that has panniers with it, but no luggage racks! are the luggage racks speciifc to the st3 or will st2/st4 luggage racks fit?
I don’t know whether they are interchangeable, but about 2004 Ducati changed from non fango to Givi. I had a 2004 ST4, which came with Non Fango panniers, I couldn’t find a matching top case, eventually I bought a Givi from Ducati Bridgewater.
The parts fiche shows the part numbers as 82912061a and 82912051A. Searching these numbers shows that they will fit back to the ST2.
So Givi says 675F is the correct mounting bracket for a top case, but Givi also says it's not compatible with the original panniers mounting racks. this guys shows that DIYing a little support for the GIVI 675F makes them compatible with the original pannier racks http://christian.giupponi.free.fr/top_case.htm