I decided to make the vertical links out of 1" bright bar to fit the M12 high tensile bolts that I'm using for the king pins (plus I already had a length of this that I bought to make the rear axle from). By making them to fit I could ensure that there was minimal play in the king pin, and I could also machine them to length so that they fitted perfectly within the hangars I had previously made.
I set the length so that two thrust washers would fit above the vertical link. These washer will help reduce friction and make the steering a little easier to turn.
After stamping the hangers and vertical links with 'L' & 'R' so I knew which one went where, I then cranked up the TIG and welded them up. Hopefully they are strong enough.
Next up I need to drill out the hangers for the king pins and weld some retaining tabs to the pivot bolts to retain them in position. I'll also add some grease zerks so that they can be lubricated, once I've figured out the range of movement.