I can't tell you piece by piece, year by year, but this is the generalized version:
Custom was the low end and pretty much means no side trim and a plain chrome strip across the dash.
Adventurer was mid level trim and included the upper side spear, tail light surround and a wood grain strip across the dash.
SE was top level trim and included Adventurer items plus lower side moulding, woodgrain dash face and longer door panels with carpeting along the bottom.
As near as I can tell, 80 / earlier Prospector package was a custom with a side spear but none of the other Adventurer items.
I think the woodgrain door panel insert was part of the Adventurer package in some years, part of the SE package in other years. Pretty sure the aluminum tail gate insert was SE only. I also think Custom was low back buckets or bench while SE was the optional (in lower trim levels) high backs as standard.
Try browsing around these two sites - they both have a big selection of original dealership brochures:
http://www.lov2xlr8.no/dodge.htmlhttp://oldcarbrochures.com/The 76 pickup brochure on the first site seems to have the most info.
http://www.lov2xlr8.no/brochures/dodge/76pick/bilder/9.jpg
