We have a space cab so we have extra room on the tray..6 speed auto 2013 very happy with it..also put a 100 litre diesel tank on the tray much cheaper than a long range tank
we plan to set up sound the same like you as we will have abn Engel in the back tray, having the second battery fitted in a box on the passenger side back wheel and another box on the other side so will run our caravan fridge and 60 lt engel from there having the back seat cig lighter rewired to heavier wiring in case we put the Engel in back seat. We towing 20 foot caravan fully loaded is 3000ks. the cover did have a rack but was removed has a roll bar inside as well.
we prefer the tray as we always carry extra water as we free camp and its perfect for across the back of the tray