Hi All 
If you are  ploughing the inside edge of the front wheel must be in line with the inside edge of the rear wheel this allows the tractor to run true.? 
But when you are drawing furrows or drills for potatoes  
The middle of the front tire must be in line with the middle of the rear wheels 
If the middle to middle of the front tires read 24 inches you can set your ploughs at 24 inches, ect 
The Gutbrod tractor has sliding rear axles so that you can move them to line up with the front ones 
The gutbrod tool bar comes with two ridgers 
If you are doing it up for show you can add three and see how it looks 
PS one of our shows this year  the theme is potatoes when I fix mine up I will  post some pics 
George S