RUFFAZ - I found one at the local wrecking yard specializing in any old car they can get their hands on - mostly American, but they have a foreign section as well. It is from an '87 5000 SD gasoline turbo car and cost $100 plus I am paying them $50 to remove it. I am not sure yet what ratios it has but I am thinking that the turbo ratios would probably be favorable. They also have some Adudi 5000s with automatics and a Quatro which I believe yields a transaxle which can also be used in a 40. Good luck.
There are a bunch of them in wrecking yards, seems in NC they range from around $175-300 depending mainly on the yard.
I can give you the number of a yard here that I know has one more, I think they want something like $250 for it, just call and have it shipped. I've looked at it and it seems good, stored indoors and good input spline. Surface rust on output flanges. Wake County Automotive in NC, located near Raleigh.
I just didn't get it as I found some that were just as good for $200.
I've got a 5N and 3U, but want to keep both. 5Ns and AAZs are the only thing in the States that I know of.