Okay, I did some googling and found a site that has chassis info for '73 - '87 Chevy trucks. Here is the link...
http://www.chuckschevytruckpages.com/framespecs.html
And here are a few pics from the site...
Like I said, I live in a unibody world. So this stuff seems utterly alien to me. Lots of Porsche folks stiffen their chassis using semi-tube frame structures. But this ladder frame thing is Model T technology. I assume the goal would be to connect the suspension points and tie them in to a full roll cage. Then somehow link it all to the engine and tranny mounts and the body mounts? Damn, this thing makes no sense to me.