I bought a Smittybuilt roll bar back in 74. It has those same piece. The Roll bar included four angle iron pieces that bolt to the those straps and then you drilled holes thru the top section of the tub where it's boxed. Requires long bolts to go thru that section. Once bolted together with the plates under the wheel well it was very stout. I put the vehicle on it's the next year and it held up well. Better than I expect a stock roll would do. But in the early eighties I replaced it with a stock roll bar because I switched to the 74 to 78 style seats front and back. I've kept the wheel on the ground ever since so not sure what it would look like laying it on it's side. I try to learn from my mistakes and on this one so far so good.