What I meant to say ( in my usual clumsy way... ) is that the $375 could go towards the locker rather than a "spare" diff.
Here's the overview - the Feroza front diff is almost identical to a Sierra rear, in fact sitting side by side you would confuse them, right down to the bearings sizes, width etc etc.
However the Feroza crownwheel has more bolts than the Sierra so we can't simply use a Sierra Locker ( and we looked long and hard but.... )
So the go is to use all the internal bits from a Sierra airlocker fitted into a new housing. The Feroza axles are bigger than the Sierra so the Sierra side gears are re-splined to Feroza spline ( a very odd spline which we FOUND a broach for by accident ! ).
Whilst we are at it, the new centre will be a solid one, without the "windows" in it that substantially weaken the Salisbury design and a 4 pinion carrier instead of the 2 pinions the Feroza has. This makes the diff SIGNIFICANTLY stronger.
So basically what we are casting is the diff centre and cover plate and using Sierra internals as noted above.
So at the end of the day you disassemble your diff, take your existing crownwheel off and fit it to the locker center and put it all together again.
Its still a significant job - but......
Oh and almost forgot, the microcat is large, about 19MB so getting it to you is going to be difficult......
Are you using an "smart" download system - one that can resume from partial downloads, might be the answer....
Firefox's DownThemAll is one such, but I'm sure there are others