TOPIC: Steering system

I'm thinking about replacing my cable/pulley system with a rack and pinion/rotary system (1960 Merc 300). I guy on kijiji has a bunch of them for $100 each. I'm assuming this isn't a bad idea (please let me know if it is). My intention would be to somehow use the existing original steering wheel. I just wanted to confirm that I'm correct about the diameter of the.......?rod? that goes through the steering plate on the engine. Is half inch correct?
Thanks

If your motor has a different size hole than the cable I have an adapter to make it work. And yes it is the best idea for your boat.