I'd recommend going with dead rock, in such a huge tank you don't want to invite any pests, aiptasia, nudis, flats, mojanos, bubble algae, etc. You'll have a huge nightmare and have to deal with it in such a huge volume.
With dead rock, you can do as you please without having to worry if you introduced pests or not. If you take a look around these threads, there have been a large amount of folks introducing dead rock only, with small traces of live rock to seed their system.
