There are very few places (IMO) that sell what is truly fully cured live rock. I have a source that I used to set up a tank several years ago, and I am using them once again to set up a 75G tank this week. (My rock order ships tomorrow). The dealer is Aquarium Arts in Bakersfield, CA. They only deal in Fiji live rock.
They do things a bit differently than most other rock dealers (again...my opinion). Most all of the Fiji Rock that comes into the US is imported by Walt Smith &Co. This dealer picks up the rock at LAX the day it arrives from Fiji. They then place it in the first of 3 seperate curing tanks the very same day. After 30 days, they move it to a second tank, and after that, to a third tank where it is housed under MH lighting. (The rock I'm receiving this week has been curing in their tanks for 11 weeks). When you purchase rock from them, they pack and ship in the late afternoon to the nearest Fedex location to your home, where you can pick the rock up. (In my case that's 9:00AM the next morning). If you prefer, they'll ship it to your house. The rock is packed with heat packs in styrofoam with some water as well.
When I purchased from them a few years ago, the rock I received was encrusted with Coraline, and had alot of life. Inspite of all this, my tank still experienced a small cycle from the die off, but it was very minimal. Amonia was elevated for about 48 hours, and then Nitrites, and Nitrates, but all was over around day 5. I waited another month before adding to the tank, but I never experienced another Amonia spike. This topic seems to always create some debate, but in my experience you can buy fully cured Live Rock.