Power steering was an option on the 300U. If you can find the parts, and there's the trick, you will need the following. 1. Power steering gearbox, containing the valving and actuator, off a 300U or 350U
2. Hydraulic regulator/flow control valve off a power steering equipped 300U or 350U. This valve has a priority valve in it that non-power steering tractors didn't have. It directs priority flow to the steering.
3. Hoses to hook it all up.
My guess would be that you are probably looking at $500-1000 to convert it.