Replacing 97 B-190 Water tank

[mhudon]

It looks as though the original fresh and gray water tanks in my 97 B-190 were replaced for some reason. I suspect a previous owner drove over something and they got torn off.
The fresh tank hangs down below the differential and is only 5 or 6 inches off the ground. I have an idea of how I'd like to do it but I'd also like to see how it was originally done. Does anyone have any photos, links or ideas?

Also, the fresh tank has a 1.5" vent running all the way to the top of the rig. Does it need that much vent volume?

Thanks!