You are in for a wild ride. Turkeys grow quickly and will want to be out of that brooder in 3 - 4 weeks. Probably earlier. At two weeks I move mine to some rabbit cages and keep them there for a couple of more weeks then into hoop coops on the ground. I have a heat light in the rabbit cage but not the hoop coop.
Those buggers can fly and they will do so. They will roost where they want to and leave evidence all over the place. Plus they are nosy. If you get them used to you they will follow you like puppies and poke around in what ever you are doing.
With regard to harvesting - 8 months is early. Takes 12 - 16 months depending on how much feed and free range you allow.
I have raised a couple of Narragansetts and now have 17 poults that are 4 weeks old. Also raised BBB. Those fill out fast, don't fly as much, and make a great table bird within 6 months.
Have fun. Chickens are entertaining but turkey's take it to another level.