'DL' was on wheels in '78' working up in the Hajar mountains at the back of Dubai when I first arrived there in June that year, we were flying geologists and drill rigs around, bit difficult on floats!!, pilots were Martin Bull and 'The Glove' Alan Price.
I believe the transition from floats to wheels took place early 78, there was another '55' there when I arrived (cant remember the reg) that was still on fixed floats.