I can't tell you what motor to buy, since you haven't told us whether this sculpture of yours is a 5 ton piece of stone on a 2-meter turntable or a 2 gram piece of foam on a 5 cm disc. The torque required from the motor is going to be different in these two circumstances, and the price of the former will be considerably higher than the latter.

Andrew Werby
www.computersculpture.com