The engine cradle had been cut out and re-welded in order to mount the standard Predator engine so I suspect the PO simply didn't align the axles correctly, causing the toe-out. It does look like this thing was really beat on, though; both front knuckles have been re-welded as well.Sounds like you got a handle on things. I would also try to figure out if the frame is bent and where.
I'm fairly new to steering geometry so it took me a couple of tries but I got rid of the bump steer while also getting close to Ackerman steering. I think I can completely eliminate the tiny amount of bump steer by putting the washers on the bottom of the knuckle (between the tie-rod end and the knuckle instead of between the knuckle and the bolt) but I don't think it's enough to worry about currently.
The next thing to work on is figuring out how to make the torque converter drive belt last longer (Comet 30 Series). As far as I can tell everything is aligned perfectly so it might just be a consequence of buying a $9 three-pack of belts...