With manual steering it is not easy to steer since you are turning against the force of the inside wheel.
You will also wear out your tires faster on pavement.
You will be needing 2 front axels, hydrolic pump, hydrolic ram, wheel control servo.
I assume this will be a offroad only rig since rear wheel steering has had a tendencacy to drift one way or another.
Branan
Oh yea I am probably forgetting gearing issues.