you can keep the stock gears and go with a 5speed, however if you go with bigger wheels, like 33s, you would definately be better off with 5.12s. Even with the diesel, lower gears are just better cause you can go with less power, not have to feather your clutch all the time.
But dont let anyones opinion stop you, else we would all drive the same vehicle the same way. People laughed at my 4 inch homemade bodylift and 33x12.5s let them.