Just as Norbie said, you can swap just the diff but its a bit of a hassle.
I found it easier to get a sacrificial T series axle to rob all the brackets and whatnot of that, and then, using another complete T series axle as the measurement template, weld the bits onto the F series axle and then bolt that on board.
So, the diff centre, the axles and the flange plate are all different between the T and the F axle.