Couple grade 5 fine thread bolts, a way to ensure they're welded at the right angle, relative to both the steering arm and camber (if your kart has any camber, that is). That's about it. Weld, then let it air cool. Do not quench till it's below 500°.
I say grade 5 because the higher alloy of grade 8 is more prone to cracking at the weld if not done properly.