I have a 99 f250 super duty 4x4 and the front hubs went in it and the parts store says that the hubs are different on early and late 99s. I know that the springs are different but are the front hubs. Thanks in advance.

 

Auto manufacturers change designs usually year to year, but also sometimes once or more during a model year, depending on different factors like dependability, problems, parts availability and hopefully to improve function and reliability,,OUCH!
You could always check with your local Ford parts dept to confirm if there are any midyear changes. They will need the vehicle serial # to fully check and confirm if that situation exists.