It's those monster shackles dude..
They're killing your caster angle. Shims might help a little but best bet would be to toss those shackles or maybe we can shorten them a couple inches on the bandsaw. If you still wanna try some shims (basically wedges that look like thin doorstops), make sure you use steel ones and not aluminum.. the aluminum ones will bend and eventually crack. I had some in the rear of my Blue CJ before I swapped axles. They were only back there for like 2 months. When I removed them, they were bent slightly to the arch of the spring and already starting to crack at the pin hole.. next, they would've spit out from between the spring and the mount.. definately something you don't want with the front axle