That first link is absolutely scary. From the mounting plates to the braces to the square tubing used at the tie rod ends. Please people don't replicate this disaster.

The second link appears to be better but there isn't a lot of detail. What I do know is I don't like the idea of the rack mounted to the axle. Yeah you can put a slip joint on the steering shaft but the axle and the shaft are moving in different arcs which could cause some weird binding issues not to mention that having the steering shaft moving up and down could cause some issues as well. The best way to do this would be with a dedicated cross member for the rack similar to what is done with a tube chassis race car and many IFS hot rod front end systems.