49Bomb,
Yes, my '52 wagon has a '51 grill. I don't know when it was put on, but it is NOT uncommon to see '52's with a '51 grille.
Most of the chrome in '52 was bad because of a shortage of nickle (Korean war effort). They tried to use copper as the base, but I'm told it only lasted a few years from new. If my bumpers are any indication, the '52 chrome was no good. :)
If you're really hot for a '49 wagon, find a '50 and put a '49 grill on it. No one will know but you and me (and a handful of other guys).
Good luck with your search.
DCMatt