For the last revolve we used, which was not quite as big as yours, we drove it with two 5hp motors connected to 20:1 gear reducers which were then connected to the drive wheels. We used a friction drive. I don't even pretend to know all the math involved to make the system work (that is why I am not a
TD). I know that we had plenty of power to creep the revolve along with a heavy and changing load, and we topped out at a fairly high number of degrees per second.
The other thing you need to think about is how you are going to control your motors. Ideally you would want to have a motion control system, but it can be done with limit switches or just by sight and a toggle switch.
You also have lots of choices in motors, AC vs. DC being the biggest. DC motors will require a power inverter. The more sophisticated inverters will allow 0-10v control signal input, which can be useful. Some inverters allow you to set accel/decel so that you could use a toggle switch and not jump right to full speed.
There are lots of options, it is hard to know what would work best for your situation and budget. If you want, you could contact
Creative Conners Inc. They are a company that produces automation gear, and they offer consulting on projects requiring automation. You can also rent gear from them, or buy it.