For posterity since Mike's old pages are gone now and if the archives get hacked again...
apping (t'gate differences between the years); "...Amazingly throughout the number of body style changes from 78 through 96, the tailgate remained nearly the same.
You can swap tailgates between all of these years taking note of the following: I've broken down the 3 major changes into their respective years.
78-79 Type A;
80-82 Type B; 83-96 Type C;
If your swapping within the same type it's just a direct swap.
If swapping A & B you have to switch the glass and glass support brackets;
If swapping B & C you have to switch latches and striker plates;
If swapping A & C you have to switch the glass, glass support brackets, latches & striker plates..."
Source: by Mike M (MRM) at his old medicine.wisc.edu site via web.archive.net
And if both have rear window defost the connections in driver tail light housing will be there