Spindels?

No I get using a fabricated steering arm and removing the ball joint from the steering arm.

But I still do not see the reason to weld that to the knuckle. Obviously you’re going to have to fabricate the steering arm regardless. But welding that to the spindle will not have a strength advantage vs bolting it to the spindle. And actually dropping the box section for what’s basically just angle is going to be a strength issue itself with that long of a steering arm, the connection to the spindle will need to be beefy if you want it to live.

And why does using rod ends require a fabricated spindle? It would work exactly the same way with the rod end whether it’s bolted on or welded.

That’s also a ton of work to use a 9” spindle. I would think using a spindle with larger bearings would be advantageous with the high speeds involved.