Bump steer like that implies a bad alignment. What size tires are on it? Going from even 28 to 31 or 33'' tires can throw off the alignment on the TTB. Camber and toe in are the major contributors to something like this. You want a little bit of toe in to guide the vehicle down the road so it doesn't wander. You also want the camber to be almost straight up perfect, but tilted out just a hair too, though not out more than 1*.

Pulling hard to the left makes me think you need to be checking your brakes and the left front wheel. If the camber is out on the left front wheel, it'll pull to the left as well.

Also, are you taking it to a 4x4 shop and not just some general alignment shop?

Check the brakes on the passenger side too, as well.

How are all of your ball joints? How are the knuckles? How are the wheel bearings?

Has the rear axle been messed with? You want to have the rear tires tracking the same as the front tires, or a wobble could occur at higher speeds. Likewise with the front suspension. Is everything spaced out evenly? It might be time to bust out the tape measure.

Ever been in a wreck? How's the frame?

You don't have the hubs locked in the front, do you? If one hub is engaged, it could possibly cause funny problems, but I highly doubt this.

Bled all the air out of the lines to make sure you're getting equal braking force to the wheels?

All 4 wheels balanced? Are the rims bent?

Cracked frame in the rear? Broken springs?

How are the shocks? Do you have sway bars?

I can't think of anything else, honestly. Let us know what you find.

EDIT:

I wonder if someone had the camber bushings changed in the front end at one point, and they were mismatched bushings or bushings that would get the wheels right in the air, but too tilted in on the ground or too tilted out.

 

I'm currently using the 2.75* fully adjustable 2 piece bushings. I've taken measurements to make sure the front/rear end is square. Leaf spring bushings are new as well.

Shocks are new, but the coil springs are original. I'm running 31x10.50 tires witth no lift.

 

I honestly can't think of what the problem could be.

The only thing I can think of would be a bent frame or a cracked frame somewhere.

Maybe check the body mounts all over the truck?

Are the steering column bolts for the steering column tight?

Puzzling.

 

This is not something that will show up during a normal FEA. A bent knuckle will also effect your toe out on turns. It's hard to tell which side is bent if it's out of whack. Check the distance between the tire and the knuckle where the outer tie rod attaches. Both sides should be the same.