Les,
I couldn't find a P/N on my grille so there may not be one. However, the easiest way to tell a 67 RS Grille from a 68 is to look at the horizontal bars. If they're the same level as the vertical bars, it's a 67. If however, they extend about about 1/32" out from the vertical bars, it's a 68. (This was where the chrome hotstamping was applied and it made it easier to do if the horizontal strip was farther out from the rest of the grille.) Also check your headlamp doors. If they're the 67 style (both horizontal and vertical strips the same depth), you might want to pull one and look for the P/N on the back. It'll be either 3898136 for the passenger's side, or 3898135 for the driver's side. Be carefull when you unscrew the 4 screws!! I broke one of mine in half from the build up of rust. (Luckily I was able to use some penetraiting oil and an extractor and get it out.) So you might want to spray some PB Blaster (or equivilant) on the threads before you remove them. Easy to access since they go through the metal door housing...
I agree with Steve regarding the weathering. I examined my grill from stem to stern and there's absolutely NO chrome (hotstamp) anywhere on it. You would think that there would be SOME reminants left, even after all these years. After all, the chrome (hotstamp) on the "SS" emblem is still there...
Rich, let me know if I can be of any help on this one. This is getting interesting!!
Ed