HI, IF YOUR CHANGING OUT THE "VALVE BODY" THEN I WOULD PUT IN A NEW GASKET. IT SHOULD COME WITH ONE I WOULD BELIVE. IF YOUR TALKING ABOUT THE TRANS PAN THEN THE GASKET IS REUSABLE. IF YOU HAVE THE 4 SPEED OVERDRIVE TRANS THEN IT WOULD BE THE MERCON 5. IF ITS THE 5 SPEED OVER DRIVE THEN ITS THE MERCON SP FLUID. I WOULD GO RIGHT TO THE DEALER FOR IT. I HAD A HARD TIME TRYING TO FIND THE SP AND THE TYPE 5 TO A DEGREE, THE DEALER IS YOUR BEST BET. KEN