11 Nov 2021

OPGI was not particularly helpful. They could just tell me that the kit contained front, rear, and middle braces. I'd have thought the middle brace was the one I needed:

(random picture from the interwebs, don't know source)
I think the unknown "middle" brace is for a Chevelle (see this Chevelles.com thread with a pic).  Regardless - the set got returned.  It does not appear that the middle brace I need is being reproduced, nor the equivalent for the longer-roofed vehicles.

So the logical next step is to make my own.  It ain't got to be pretty.  Cut a sheet of 22ga (I'd have preferred 16 or 18ga but didn't have it big enough).  That strip is 3" wide by 27" long.
Cleaned up the edge a little with a file.

Used the flanging tool to put a nice bend on the edges to add some strength.
Test-fit.  Cleco at the back, front wraps around a flange.

This needed to have more of a bow to it.
Used the bow I had in each of the holes to identify the range that was valid for each of these clips. 

Paint, too.
Test-fit.  Acceptable.
And then the welding starts.
Weld, weld, weld.  Skip around so nothing overheats.
Grind the welds.

Also I cut a small bit of metal to match the back edge of the roof to the B-pillar and welded it in.  This looks a lot better.
Started grinding the welds in the rear window area.  Ran out of daylight, more to come.

Go back to the previous day (6 Nov 2021)