The 2pt straight bar will be a rough ride and will stop axle wrap, but your material is not heavy enough. A 3pt with leaf spring shackle mount on the frame will still allow for much better ride.
Think of it this way when laying out a pattern to make a circle. You use a known distance (radius). You have a fixed point on the frame of your truck (center of the circle). Move the other end up and down (axle), the motion makes a circle, not a straight line up and down. Since your axle is fairly rigid (it is rigid from the front leaf eyes to the axle but shackles in the back), it will push the axle very hard to the back and put a lot of pressure on the front leaf mounts. That's where the shackle mount on the frame comes into play with a 3pt connection and allows the axle to float up and down. The over/under mount on the axle fight equally against each other under axle wrapping as it creates a push/pull effect essentially canceling each force.
Hopefully I explained it well enough as I'm more of a visual person. Lol.
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