I have a comment that nobody's addressing, on the QA1 k frame. I peurchased this, and installed it in my gen III duster build. When I went to install the T bars. One was deep in the cross member socket, and the retainer was a cinch to install. The other was too shallow. So the welder at our local stock car track copied it, and we returned it.
The retainer wasn't actually locked in. I had to loosen the bolts on the QA1, strap the k frame to a truck, and carefully put tension on it. The only thing keeping the k member locked in place is the torque on the mounting bolts ( 200 lbs.), and one goes through a 3 inch pipe. The rear most bolts give you no room to torque them if some problem is found after everything is installed. In that case you have to remove everything again, or fight with it. The factory piece has a conical part under the bolt head to lock it in. Although both of my torsion bars were locked in , one bar was still shallower than the other.
U.S. tools, and XV makes a stiffener for the cars frame that goes under the radiator. We saw this, and added that front piece to the QA1 style k member, it locks into two pieces welded to the frame with 5/8 bolts. The idea is it reinforces the cars frame, and locks the k member from being able to be bolted up on any weird angles, or moving by accident. The back of the frame we didn't figure out. After some playing with the damn thing, I finally got a mock up done today. One off piece, that I would never do attempt again. If the alignment guy can't align the car, I'm sort of screwed.