I have posted previously that I am going to try an independent swing arm suspension with a single transverse half elliptical leaf spring.  Basically, two swing arms are attached to mini axles that are mounted in flange bearings. They leaf spring will then rest atop the swing arms in shackles.

Front Cycle Kart Suspension

I have yet to weld the swing arms to the axles as I will likely redo the swing arm on the left as it is too far off center. I was going to use through fastened bolts with a steel box in the middle, however after seeing the amount of play in the piece, I decided I will weld the central box (not pictured) to the two frame pieces and use shorter bolts to attach the bearings.