Xtracurricular,
I am not sure if plastiguage would work to set up bearings.
I have not had any experience with diffs either before I tackled this job. You will need a service manual, couple of special tools (or you can make them by yourself as I did), hydraulic press to press bearings (or have a buddy that have one) and a friend to help you un-torque and torque bolts (air tools will not work – sockets are two thick (wall) to torque bolts of arb diff case with ring gear – I tried regular sockets and I busted two of them).

It took me about one week to install the locker (evenings after work). Compressor, air line and electrical stuff took another few days. I have a picture of every single detail of the install so I you need any info let me know. I have learned a lot and it was a good project.

Brent,
I have read replay from the ARB guy and I disagree with most he said. This is my opinion and I am not trying to convince anybody to polish the shaft or not.
Here is what I found interesting from his replay:

“One major concern in this practise is the effect that polishing will have on the bearing seat.
This area is precision machined for optimum fit of the tapered roller bearing cone and polishing it would undoubtedly destroy that fit, resulting in a spun/destroyed bearing.”
My comment – I was polishing the area where o-rings are seated NOT where the bearing is seated. Look at my picture of the polished shaft – the bearing seats below this surface and it is NOT polished as you can see. Besides I measured the shaft before and after polishing and I was not able to measure any difference with a caliper (resolution 0.01mm). I’ll bet the shaft after polishing was within tolerances they originally specified.

“Secondly, the article does not make mention of exactly how you managed to remove the abrasive grit which would have been dusted over the outside and inside of the differential and certainly would have entered the air hole in the journal and contaminated the air system. This would definitely cause O-ring failure and wear/damage to bearings and gears if it was not cleaned out. “
My comment – I made sure to not make any dust. I “wet” polished the shaft (notice the oil bottle next to the diff case). Just in case I put the red plastic foil but there was absolutely no loose particles and you would think everyone would do this way.

“Lastly, but not least, the compound used in Air Locker O-rings is called 'Viton' and, although more expensive, it is a very hard wearing, durable, heat resistant elastomer, and you will find that after you have completed only a few hundred miles, the O-ring has actually polished the bearing journal for you in exactly the right two spots. In fact, it is this break-in period when the O-rings rub against the machined surface that the fine mould line is removed from the O-ring surface as well. We have found that polished surfaces will not remove this O-ring mould line for a significantly longer period of running.”
My comment: Fluorocarbon elastomer (DuPont trademark: Viton) is not as hard wearing as he thinks. There more durable elastomers such polyurethane, NBR, HNBR etc. The biggest benefit of “Viton” is that it has good high temperature capability and is compatible with various oils. ARB guy’s comment that after break-in o-rings rubbed and polished the shaft gives some directions here. What do you think gave first: steel shaft or o-ring material. I have not seen any excessive parting (“mould”) line on the provided o-rings so I do not really get his last comment.