GMC front end differences

[bama51]

I know this has been discussed before, but my searches returned to much junk to filter through, so I'll start this discussion again.

What are the differences in the 67-72 GMC front ends? Obviously the grills are different (look different, do they mount different?), but what about fenders and hood?
My reason for asking is that I have a 72 GMC, complete with chrome top bar and eyebrows and a painted grille. I want to change the grille to chrome, and I really like the look of the 67 GMC grille. Will this grille mount up correctly to my 72? I know the purists out there will say that you must remove the eyebrows and change the top bar, but is that true? Any help would be greatly appreciated.

Chris