If he's helping you with it, I guess I'd ask him; if he has the background you say, he'll know where you can put your hands on one better than we will.
While I understand the basics of how to set a rear end up, I always pay someone that has done it a bunch of times to do mine. I don't have the tools needed (presses/pullers for bearing removal) to do the job.
Summit sells a tool by Proform, that includes the dial indicator, the jigs, and the extensions, for about a $100. In their catalog and on their website.
I just finished doing one the hard way. I cut a piece of aluminum angle and made holes to bolt in on the differential cap bolt holes in the case, and a hole over the pinion head. Had the face of the angle surfaced at a machine shop that does heads, to make it flat. I used a dial caliper, the extension end, to measure through the hole to the pinion head, and subtracted the angle thickness.
That gives the axle/differential centerline to pinion head depth. Took four tries, pressing the inner pinion bearing on and off, but it is within .002 by my measurements.I put the stock differential shims back in, and have .008 in backlash.
The contact pattern looks ok, maybe a bit too toe oriented.
I am going to sleep on it and see if I think it is ok, or maybe subtract a couple thousanths of pinion shim and try again.
It helps that I have a homemade case spreader that bolts to the differential case bolt holes, so I do not have to hammer the differential shims back in. That would be the most difficult part to me, especially with the aftermarket stackable shim packs.
I will probably buy the tool soon, just because, after three of these, I want to do it a bit easier.
I made the case spreader from a piece of 1/2 in plate I found in the middle of the road, a turn buckle, and a piece of angle. I laid out some c shaped pieces to fit over the diff cap bolts, with enough space for the diff bearings to clear and go into the case, two straight pieces for the spreader. At that time I did not have a torch, so I paid someone $35 to cut the pieces. I bought a turnbuckle, some 4 inch long, half inch bolts, and made pipe spacers for the bolts. I drilled the holes at home. It fit my 7.5 in axles, and fits 8.8's also. It is somewhat cumbersome to put on and take off, and the 8.8 bearings don't fit through it like the 7.5 did, but it has been well worth it. Just got done using it a half hour ago.
If you use the stock differential shims and lots of care, you can tap them back in, as lots of people do this. If you use the stackable shims, it is hard to tap them without damaging them.
Actually, crushing the crush sleeve was more difficult than anything, took a half in breaker bar and a 2 ft pipe extension.