Lots of good info for sure. Just a reminder for those taking notes..
The driveshaft length quoted herein will vary with which rear end is used.
Measure what you need for your build.
Yup, the only way to be sure. I'm only mentioning them in this build so I don't forget ;-) Of course if you have a Duster with an 8.25 rear and spool mount engine with factory mounts the length should work for you as well.