I hope that you have been enjoying your Overlander since you replaced the axles. It looks like a carbon copy of mine from the picture.
I did order the #11 3500 lb axle and those came standard with the 12 inch brake drums. Also ordered them with a 32.5 starting down angle. The brackets seem to be about 10 inches and fit extremely well between the frame rails. The tube is 3 inches and that is why the frame rail cut out needed to be enlarged. I made the cut on the rear of the opening so that the alignment would not be affected and the front of the cutout stayed original to the OEM axles. The old axles were 2800 lb axles and I think they had 10 inch brakes. I got $3.75 from the recycler for them so too late to actually measure them again! And they were 240 lbs each! Back breakers!
Once I knew I needed new axles I was all over this forum and the internet reading and learning from others experiences with the axle replacement. That is why I went with Inland RV, 32.5 down angle, #11 3500 lb axles with 12 inch brakes and decided to keep the shocks even though many say they are not necessary. The engineers did so why not just keep it simple and replace as original.
You are just down the road! I spent 4 months in Northern CA in our baby last year working for the USFS and hope to do it again next year. When the season ended we took the southern route back to here and went through Sequoia National Park, Joshua Tree, Prescott, AZ and then down to San Antonio before heading north and getting into CO on Nov 7th.
Now doing some maintenance and small repairs to get her ready for next year. I am also on the lookout for some used aluminum AS wheels. I found four of them in East Texas so that might be the next little addition to the girl.
If you need something drop a note...I am off til April!