98+ 626 rear's are a bolt on upgrade. Never heard of the millenia rear set up being used anywhere before.
Im running the mazda6 front set up, and the 98+ 626 rear's on my own beater with great results.
and im 99% sure you could make the mazda6 rears work, including the ebrake if u used the 98+ 626 ebrake cable, as the 98+ 626 is a few inch's longer then the 93-97's. and the entire issue using the mazda6 rears is our stock ebrake cable is a few inch's too short.
Ive covered this a few times, in a few threads, on a few forums. But no one has tried it yet.