And even more ...
Here is the support at 9 degrees with two of the flanges welded to the bottom rail.
I should have posted this at the beginning of the topic ... but this is what the modification is based on, from the 69 Assembly Manual ... these construction drawings obviously show the core support should NOT be straight up and down, but has a pronounced lean towards the front at the top. As verified by owners with assembled original cars.
Will try to finish the project in a timely manner and get the rest of the photos up.
In the next installment of this "how to" I will be fabricated some splice plates for two more spot welded flanges, and the main braces.
So far so good .... assuming I haven't made a gross misconceptual error about how this part was supposed to be manufactured I should be good when it comes time to assemble the front end.