Dana 60 questions
To answer your specific questions in this thread:
Unless you want to try a set of my prototype 3.23 Dana 60 gears, since you are running a short 25" tire and a low 3.09 first gear, I recommend a 3.54 ratio.
I recommend the S-Trac helical differential, as it is super smooth, quiet and good to 1000 HP.
I also recommend 2" wheel studs, because the 3" version will not fit a common wheel spacer as mentioned in your E-mail.
An S-60 assembly is custom built, so you can choose the ideal width. This depends on your wheel width and backspacing, however. For example, a 10" wide wheel with 5" backspacing fits a '65-'67 B-body width (54.25") housing and my 1" offset spring hanger/shackle kit when installed in an E-body. I can alter this once I know your wheel dimensions.
See below for options and pricing:
Strange S-60 for Mopar, Ford, Chevy/GM
Thanks,
Cass