Help please: search V8 4.2 for buy

Hello everybody,
Happy owner of an Audi 100 (type 44), I'm searching now to buy a V8 one, 4.2 liter if it's possible. What are details to verify on that model during buying, what are prices for model in good condition of year 90?
In France it's too difficult to find a V8, moreover in good condition, so I'm searching in Germany, Belgium maybe...
Thank you for replying