The engine mount/driveshaft setup is the same on most XUD pugs and citroens as well as the Dw10, it would be interesting to see if the 407 retained the same layout, and on the topic of parts sharing i found that part for the exhaust manifold was used on the 405, 309 and 205, its called an exhaust muffler:

It costs about £18 from peugeot, euro car parts have it on sale at the moment for £25, and failing that i drew it up on solid works last night:

and could possibly get the top and bottom cut out on the plasma cutter at work, it would be just a case of finding a bit of round pipe with a 127mm diameter