Not to defend their example of crappy customer service, but some research should've quickly shown nothing they offer fits a Torsen carrier.
What I suspect happened is he ("jbrown") read your email right up to the point he saw "torsen differential", and never bothered to read anything beyond that.
Had you simply asked for a 8.8" 31 spline open carrier application, there would not have been the distraction over the Torsen.
Now as for the rest of it, there's no excuse for that, he could've simply scrolled your email down a little ways and reread your questions (this assuming you didn't delete/backspace out the previous correspondence from the email)
Since you have to get a carrier for yours anyway, I'd just buy the Detroit.
To the OP,
I'd say maybe rebuild the stock L/S, but rearrange the clutch discs for tighter grip (there should be some info on this in the Tech Library). Combined with using slightly less friction additive, you can get some pretty darn good lockup out of it, but without all the clunkiness and unpredictability of automatic lockers.