'67 Dart with '68 idler arm?

OK, I'm leaning towards getting the correct '67 arm but that's an interesting point about the hole possibly being drilled out. Does anyone know for sure if that bolt would have been larger than the fixed one on the '67 arm? Another thing I forgot to mention was that the car does have early 70's disc brakes grafted on. Also what that bugs me about this mod is that the top nut on K member side has no cotter pin.

I see that Jegs has a '67 arm so I suppose I'll go with that unless I hear otherwise. Thanks a lot for the help.