3. Your spring plates may need to be modified to fit the new u bolt width, ie slotted or hit a boneyard to find one that will work. If plausable move brackets from existing rear for shock mounting.
4. Measure your spring width then your tube diameter, several sources both on ebay or Summit and Jegs with new perches. I got mine off an old truck 9" I had laying around.
5. If you take your time and have a steady hand use masking tape to mark it square and use a cutoff wheel on angle grinder etc.
6. There are apps for your phone that are angle finders the angle is a combo of your output shaft angle and pinion angle. Others can get you in a ballpark with #'s