I was kidding about the pic (sorta
). That jumping around sounds like you have bigger issues than the steering box. Seems you have play between the tires. IF it were the box, it wouldn't be pulling different directions.
Jack the font end off the ground, grab a tire top and bottom, and see if there is any wobble. Grab at 10 and 4, and 2 and 8 also. Try the other side. Should be no more than a 1/4" movement at tires edge. Then go through and check all your linkage. Put one tire down and try moving the other side to side. Really shouldn't be any movement there.
If all is good, recheck your toe. Also check all your spring and hairpin connections.
My F100 has a wormed out hole in the axle. It'll do the same thing. Pulls a little right, but going around a right turn it'll flip left then back right after I straighten out.
Also check the bolts that hold the kingpins in place - might wanna do that first thing since they are new pins.