So, an update.
I eventually had to go out of the country (fortunately I live pretty close) to find someone willing to do the differential work. I called probably a dozen shops in WA and most just weren't set up to work with a truck the size of the deuce and I only found one that admitted to working on Rockwell 2.5's. There was one shop that sounded promising, guy said he'd even installed ARB's on Rockwells about 15 years back but when I called them back they said they could do it, but didn't want to do something they don't usually do (wtf?) - that was Randy's Off Road.
The guy I did find is in Mission, BC called Enrico's Differential Solutions. He's was recommended to me by 2 other people (competitors) in lower BC and no one I'd spoken to had worked on deuce differentials but this guy was said to have worked on hundreds of ARB's. His shop wasn't big enough to pull apart the deuce so he set me up with Mid Valley Drive Train, a commercial shop near his that would rip apart the axles, give him the differentials then put everything back together.
So, apparently, while Enrico was working on the diffs he found something wrong, contacted ARB and they paid him to fix it as warranty work. He told me working on the Rockwells took a lot longer than any other ARB's he's done, so I'm glad I went with a pro - also I wouldn't have found the fault until something went wrong during operation. In the end he charged CDN$460 (~$350 US) for each diff. I asked him if he would rather not have me list his name on-line, I really got the impression that this was a PITA job for him, but he said better him than some someone that doesn't know what they're doing. I know he spent 2 days on the first diff, that was discovering the problem and communicating back and forth with ARB and probably a 3rd day on the 2nd diff.
Mid Valley has been busy so they haven't gotten back to finishing me up, they're keeping it inside and I know they want the bay back so I think I'll get it back fairly soon.