Since you asked.... I would (did) distribute the batteries and put most of them under the box between the frame rails. The truck will handle much better and "feel" like you are not carrying a load at hich centre of gravity. I would put some under the hood, some in front of the rear axle and some behind it. This will give you good weight distribution, a safer handling vehicle and the ability to use your box for other things. Yes, it is more work. A lot more work... but the better choice IMHO.