Wow those look horrible. I highly doubt mf and the suggested above compounds would completely remove them. In fact I am pretty certain they won't.
I must ask, if the owner of that vehicle plans to engage in this type of offroad activity, there really is no point or sense in buffing it. All you will do is remove paint and it will get scratched again.
It's like a mountain bike that gets taken on trails, it will get scratched and scuffed. No sense in "detailing" something like this, unless he plans to sell it or not go on those trails again.
But to answer your question, I would grab a wool pad and some 105 or Power Gloss and see what happens. You may need to wetsand the entire truck with 2000-3000 grit before buffing depending on how deep those are.