Auto Edge is a great place and could probably easily handle anything but they are Porsche 951 gurus and may not want to dable with us given the rest of their business demands.
If I do a diff for this car, and I want to,, I will talk to an old VW freind at South Central Imports, SCI. Chad is a brilliant mechanic and has done a million VAG Quaifes, Peloquins, Wavetracs etc. Guy actually enjoys the challenge of diff installs I think. Ita a great shop and he is a gifted diff and transmission type guy in particular.
Would need to have a conversation with him and prepare as I am sure it will be foreign to him but there is nobody I would trust more for something like this.
*I have had a couple Quaifes installed and should have had them all installed at SCI in retrospect.