Go to a race track and look under all the cars. Ford 9" is the majority choice and there is a reason for it. They are hella stronger & cheaper to build with better gear selection than an 8 3/4 ever had to offer and easier gear swaps than a Dana 60.
They are easier to build due to the huge aftermarket, have more gear ratio selections (from 2.40 to 6.50), and all sorts of aftermarket parts. That's it. Note that many "Ford" 9" axles under race cars have ZERO Ford parts! (Just like a drag "Powerglide" uses no factory parts.)
For an A-body, I would rather have an 8.25" Chrysler than a 9".
