Yes, 6408d dose work with 7.05, as well as 6416, 6424. I had them working on DS16/DS30 on both 500, and 406v2. The 6402 is still blocked, and will not work. Should also be ok with 7.12
Avaya no longer supports 64xx on R7, so if You encounter any problems, Your on Your own.
Amriddle has a good point, these are old phones. Just show them 96xx, 95xx phones, and most People love them!
Andre