https://tanisgoff.smugmug.com/Jeep/
dig through these, you can see how it turned out.
When we done the rocker replacement you cut the rockers flush with the edge of the door frame. then drill holes every 3-4" and use those holes to weld a piece of 1/8" steel to the underside of the door frame.
Then underneath you weld in a piece of 1/8" angle to the unibody. it essentially makes a shelf for the 2x6. where you put the angle determines how the 2x6 will sit (flat, angled up, or down)
when you weld the angle in, use the same plug weld method (drill holes every 3-4" and weld it in. paint everything, mask off where you'll be welding in the 2x6.
measure half a dozen times and cut ones for the 2x6, we used a portable bandsaw which worked great then made 1/8" plugs for the end of the tube. paint the 2x6 yet again masking off where you need to weld. have a helper sit the 2x6 into the shelf you made for it, tall jackstands work great to hold it there. then burn it in. I would also recommend making some outriggers that go from the unibody "frame" to the 2x6 for extra strength.
if your welder has a hookup for a tank, get it. flux core will work but using shielding gas makes so much cleaner welds. ive had my rockers for a few years now and they have never taken damage, and they have taken hard hits. I would also recommend using a brush on bedliner as it goes on thicker.
ill get into my laptop tonight and find the few pics of the install.