Guys, many of you have more experience with these rears than I but I wanted to bring up a couple of points. I was at a seminar once that DTS put on and they mentioned that Dana axle tubes were not very strong - thin wall mild steel and some people were having problems bending them -They had a process where they would mill out the tube welds in the case and remove the stock tubes and replace them with chrome moly thicker wall tubes and weld them back to the case in the stock locations as well as a full weld where the tubes exit the case.
I would think that the length of the tubes as well as where the suspension components (leaf springs, ladder bars, ect...) attach also would play into the bending of the axles. A shorter rear would be stiffer.

I also am tired of hearing that a 9" is the only way to go especially on street & street/strip cars. My argument is that you can build a Dana that is basicly trouble free for a car up to the 9 sec zone with mostly the parts it came with - add a steel cap, gear and axles and you are ready to go. When building a 9" Ford you need to replace almost everything in the 3rd member, case, pinion support, ect... as well as brace the housing - Is it stronger and lighter than a Dana, Yes, but also more expensive for this type of car. Unless you are running a class car, an extreme HP car or possibly a really fast car on Drag Radials, I don't see the need to HAVE to run a 9"
Just my 2 cents