I thought the nutserts were only for the after market fitting option, but the Chrysler Voyager roof rails are fitted using them as OEM ! On the 300 tourer the roof lining looks as though you could lower it enough to get your hand in with bolts which agreed would be a better option !
As for using a pair of rails from another doner car, yes it could be done, the Audi A4 rails (look similar to Chrysler )are there on fleabay as is the Citroen C5, in fact the C5 look alot more aerodynamic, which may be quieter ?
But one thing to keep in mind is that the Voyager and probably the 300 as well as most others have a strengthening plate where the roof rails bolt to, fitting a non 300 rail set that doesnt sit in the same place may mean your drilling in a single skin area ?... just my thoughts !
And Simon didnt really want them on ! lol