Ready made spindle kits are available! I sell the Azusa kits for $25 a pair.
Jig Welded Spindle Kits - 5/8" Kingpin
Bushings, spacers, and locknuts included in kits. Two axle diameters to choose from. Choice of lengths. The individual assemblies in a spindle set are designated as "Side1" and "Side 2". This indicates that one is the "mirror image" of the other to produce a set, no matter how the assemblies are oriented.
The only welding required is to weld the spindle bracket to your frame, but we have had guys bolt them on as well so they can adjust caster.