That's like 440 lbs sitting in the back of your truck and that is going to offset the center of gravity for the designed structure.
Well, talking of CG, the chop i did (chopped 225 kg's) and a winch weighing about 70-80 kgs brought the center of gravity way up front, the tank brings it to the center (full tank). I do have a 4inch lift, the rear was 6 inches high before installing the tank. The tank was 3/4 full when i took the pictures and you can see i still have a lot of clearance.
I do get a better departure angle as will be removing the rear bumper and with no tank underneath it will be slightly higher then before.
Why do you need 230 liters of diesel ? The more the better. On a serious note the local pumps here have a lot of water contamination, and the simplest way to filter the water out is to let the diesel sit there and drain the water from underneath which i can btw with a drain bolt. Water can do some serious damage when injected.