And so it begins,,,,,, 5-speed Duster swap!

Not at all. You'll find nothing made like this anywhere. You'll find a lot of C, U, H, I shapes but not this for a reason that its only stiff if it only took load in the driection of the 2" (as if it was a floor joist in a house or something) which this is not doing at all.

The tie in to the existing structure is bad, only as good as the weakest point (which is the sheet metal itself), right angles without gussets is bad, and it has low stiffness. 1/4" bends super duper easy by hand and even with double the thickness you can see it was cold bent, not sure what they used but a lever arm of a couple feet you could probably do it manually pretty easily.

The original part is the way it is for a reason. Even if this was made out of 1x2" rectangular tubing with mitre cuts and welds to get around the crossmember with decent welds it would be fairly stiff.
My plan is to take two stock upper cross members, section them and make a larger one.