If you don't have a way to check pinion depth, use your old ones. They should be about .030 thick. On the pinion look for markings of + or - 1 or 2. That means you need to add or subtrack that from the number on your shimpack. That should give you a starting point. Install your pinion with the inner brng and outer brng and slinger and flange, and OLD nut. Torque to rotational torque spec given for that, I believe 16 to 19 in/lb. Install center section, set backlash, do pattern ck if ok thats the only way to verify pinion setting is proper without depth gauge. Then install crush sl,
oil seal, new nut, torque etc.
The S springs in the track lock can be tricky to get back in also. There is a little trick though if you get stuck.
Don't beat yourself up or get frustrated, take your time, feel free to call. or whatever.
John.