Military rear cross member

[Bigdog]

I assume the military rear cross member is different from the one I have

[Davidss]

Yes, but, there are some practical effects to be considered before you make a final decision. Which of these considerations are most important depends on you, the user.
Your image shows a civilian cross member, the most obvious tell tales are the end sections being tapered in height, and the centre section being 'tall' in height; tall being a relative term in comparison to the military cross member.

The military version is the same height along the full width. It is sized to take the NATO hitch, which will end up close to the height of the tub floor.
The lower edge of the military version gives greater ground clearance, therefore a better departure angle when transitioning from level ground to an upward slope.

If you are using a Nato hitch, and trailers with the appropriate ring hitch this positioning of the hitch doesn't matter.
If you intend using the civilian standard 50mm hitch and trailers, the hitch will have to be a lot lower than the cross member so you will need a very long drop plate. This will hang so far below the cross member that in use the member will flex along its length between the chassis rails.
How much it will flex will vary dependant on the towed weight, the unevenness of the terrain, and the speed across the terrain. If too much flex takes place too often the cross member will fatigue, crack, and fail.
Only you will know the conditions of use.

That's my starter for 10.

[Bigdog]

Thanks Davides