Both are BKH series engines, wrecking yards usually know but then again they want to sell engines. Any differences (exhaust manifold, sensor locations. I just looked up a random item, the valve cover gaskets both years had identical. Maybe go to a website like www.rockauto and compare engine mount, intake exhaust manifold gaskets, fuel injectors see if the external parts are the same/will mount in the same places. Perhaps post your question on an Audi specific website or A6 website, those guys are certainly enthusiast.