One step forward, 2 steps back.
I've still been @ it but haven't really made 'progress' because I'm doing stuff twice. I was reading through various threads & came across one for "c-notches"....
http://67-72chevytrucks.com/vboard/s...d.php?t=393867
There was some excellent info being discussed & shared & board member Lakeroadster helped several of us out w/an engineering perspective. With his input, I realized the c-notched area of my frame was much weaker than stock (which is much weaker than I anticipated).
I figured that modified area of frame would be about the same strength as stock w/the thicker .250" material for the home-made notch & the inside boxing. After running the specs through some calculations, the results were scary.
So, I asked more questions & started contemplating various options. I went ahead & cut up the same area on another frame to get the contours necessary to build a 'truss' section above the c-notches. This will add the much needed height for strength while keeping the flow of the frame.
I did a bunch of measuring, cutting, measuring, cutting, grinding, measuring, grinding..... well you get the idea

. After all the effort, I have the outer portions of the trusses complete & tacked in place. I started cutting some re-inforcement plates that will be welded in between the original frame & the new sections to help tie things together better. Hopefully I'll get them trimmed down for a good fit & start welding things up during the week.
All the various clamps & steel is to ensure the new sections are square w/the top of the original frame while remaining square to each other. The proof is in the pics....