The cabinet of 6500/7000 is identical, also inside the deck. But not the 5500, it's completely different, inside and outside.
All drives are different, 5500, 6500 and 7000 are NOT identical. 6500 and 7000 look quite the same... but it is not the same. The board on the drive ist different and the cable connector is different (180 degree mirror). If you try to connect a 6500 in a 7000 you will have a firework... or you exchange the drive and the cable!