Orv, I am questioning whether I was right or wrong on that info. I had just been through a "build your own truck" exercise online to see what the new F350 might cost me this summer and had noted only the 3.73 axle was available. However, I was "building" a single rear wheel F350. I think the 4.10 and 4.30 may be available in the dually. And I think in the V10 SRW. I now will have to research this further to confirm or correct my statement.
Did a little research.
The following link is to a snipped portion of the 2008 Ford Towing Guide. The picture is too big to post directly and I couldn't make it smaller and still be legible. You can clearly see the 3.73 is the only axle available with the 6.4 diesel SRW but the other axles are available with the dually.
2008 Ford FW Tow/GCWR Ratings