I don't think you will see positive caster on any car, unless it's made to spin. Positive caster gives you the steering pivot point behind the center of the contact patch, which will make the wheel fight running straight ahead and flop to the ends of steering travel, putting you into the ditch or oncoming with remarkable vigor. Impossible to control. Like pushing a grocery cart with the caster wheels pointed backward and keeping them that way. Not gonna happen.

I think shimming different ways on the same side two bolts that hold the a arm pivot shaft to the frame is doodoo. It's not made to bolt up like that. The arm will be cocked on the shims, and the bolt heads won't sit flush when you tighten it up. Looks like a dandy way to lose shims as it loosens up. Run away...