They are the same chassis and pump and motor like tazz said. One a 742b though they went to a two piece axle which makes changing wheel seals alot easier, like a hr instead of 24 hrs of labor too change a seal.From what i can see, the 742B is the newer model, it also has a different engine to the 742.
You will find it will have the same chassis, same pump/motors. For the most part it will look exactly the same, the “B” is just a later model.. I believe the performance will be exactly the same.
I hope this is what you wanted to hear.