Not the shackle flip. Here's what I would do, take off the steering damper then drive it. See how it handles. You can better evaluate with the damper off. When I evaluate steering problems the damper is the first thing I take off and the last thing I put back on. Also check the frame for cracks around the gearbox, they crack there. Most likely a combination of: Ball joints, steering gear, body bushings, suspension bushings and so on. Each component contributes to poor handling. I can't tell you how many people yank on their ball joints and deem them "Aye Okay"! I think the 35" tires and all the shocks are a tell tale sign... some thrashing was done. No biggie, you just need to replace some parts. Start with the ball joints! Your problem sounds like something is binding then letting loose.
Most likely a worn part. But pics are good, maybe someone here can spot something that is misassembled.
j