6 bolts which can be studs and nuts hold the two boxes together 2 from front 4 from rear ,two dowels hold them inline and must go back so check as you cant tell which box they will stay with +linkage which will be self evident ,i fix the two together and set linkage before fitting as is easier imo,to do this stand t/box on hand brake drum and support pto cover and lower gear box down vertically into t/box ,if your old is defender lt77 and not scrap i would be interested,no gaskets or sealer are needed to fit t/box to gear box or gear box to engine