Check the rear pillars for hinge slots. I did this conversion on a 77 Burb. The body was made for either barn doors OR a tailgate. If the hinge slots are there ( 2 each side), you should be able to do it. I had to purchase a new sill plate from a dealer. The sill plate for a tailgate will not work.
The actual changeout was a little scary. After cutting the original sill plate out, I had to spread the rear of the body apart with a high lift jack to insert the new sill plate. Thought for sure the glass would blow. Once the sill plate was in, the rest was a breeze. Hope this helps.
GA