Thanks Pete, yes that was my understanding too, a bit off each side.
The diff housing isn't the problem, its the axles as they fall into the category of not been long enough to shorten and to long to use.
Apparently you/they can't just cut the axels and re-spline them. But I thought this is what they did to shorten diff's.
The guy I got to do the diff is a diff engineer specialist, Geoff England. so I think he knows what his talking about.
Admittedly he manly does ford stuff, not much Toyota's.
My new way of thinking is maybe getting custom axles made up?