http://www.victorypp.com/inventory/37
Not necessarily a recommendation - just an observation. Victory Performance (and I'm sure others) offer "ball joint ring taps". Any thoughts on tapping the upper end of the spindle for a screw-in ball joint? A good idea for aluminum? That might help control the height above the spindle that the ball joint sticks up. At one time I had also considered machining the upper spindle for a press in sleeve (with shoulder) that accepts a screw-in ball joint. A secondary machining operation could cut a recess into which you could "sink" the flange, also allowing you to lower the ball joint into the top of the spindle. Pressing in such an adapter ring would probably be a more precise operation than trying to press in a ball joint.
Pappy