Depends on which WG model you're talking about.
If you mean a 4900/4915 or 5501/5515, then yes you can, although there is a slight difference in the values of a few ceramic caps, but the neckboard will still work.
If you mean a k7000/K7600, then usually the standard-res has an 8-pin neck socket and the med-res has a 10-pin neck socket, plus the med-res has one of the socket pins pulled out with a wire attached - so that won't work.
If you mean a K7400/K7500, then I think they are the same and can be swapped....
EDIT - just saw you were talking about 4900's, but I'll leave the rest of it for anyone else who may wonder...