In the "body and frame" chapter of your factory shop manual. I think some of them had separate manuals for the body
The thread:
You need to scroll down, as some of the first links got broken, and were re-posted later on
http://www.forabodiesonly.com/mopar/showthread.php?t=132309&highlight=manual,+download
There's a 66 and 70 manual over at MyMopar
http://www.mymopar.com/index.php?pid=31
This is out of the 70 Dart manual: