in my '81 280zxt there is close to, if not exact, a 21 gallon gas tank. now with my z i can get 20 and sometimes close to 25 miles a gallon at 60 mph. would it be worth it to drop the tank and add a fuel cell to save weight? i know i can not fill it up all the way but has anyone done this? is there a cell that will bolt in or would it have modified? thanks for any input. bama