Confusing question, all 1st gen broncos are U-series. U150, U151, etc. So I am not sure what you are asking?
Yes, all body tubs will accept doors. But you have to pay attention to years as the door jab changed between 67 and 68, different jams and different strikers. Got to run them matched.
Almost sounds like you have a roadster and want to make it into a wagon?