I've had a few pass through my hands.The local junkyard calls me when they get something they think is A,and if it is I haul it home.30 years ago they were hauling a lot of those tractors in when the old farms were being developed.All the ones I had used a big ring gear inside of the wheel,with a pinion on the original axle shaft to turn it.As time went by and farmers were getting real tractors,the A conversions would get made into something else.They would strip it down to the frame,removing the steering,engine,trans,and rear end.Then they would use it as a hay wagon,the big rear wheels worked out well for that.The Ford rear ends were always gone,so the drive pinions were always missing.The most common one around here was Sears Roebuck,and that was the only complete one I ever had.