I just reassembled the front of my '75 Vega with S10 spindles, S10 ball joints and stock Vega upper and lower control arms. I don't have it back on the ground yet to see if I successfully designed out the negative chamber, but here is what I did:
I elevated my car (blocks under all four tires) and measured my front end geometry. I drew the upper control arm, lower control arm, spindle, with a 20 inch tall tire mounted, in AutoCad. Changing nothing else, I checked to see what shortening the spindle 1/16 inch would do to the chamber (the S10 spindle is 1/16 shorter than the Vega spindle it replaces). The 1/16 decrease in spindle height was enough cause the 20 inch tire to lean in 1 degree (and cause the top of the tire to lean in .271). In AutoCad, I had to move the lower ball joint location inward .124 to correct the 1 degree negative chamber.
With that knowledge, I installed the upper S10 ball joint as close to the original location as possible. The closest I could actually fit the larger S10 ball joint to the original was .075 away, so relocated them .075 inward.
Next, the lower ball joint needed to be moved .075 also: .075 would need to be added to the .124 (to correct the negative chamber) for a total of .199 inward relocation of the lower ball joint. I used UB Machine S10 ball joint sleeves, and had them welded in .250 inward, rather than the .199 to allow for additional adjustment, in case of a ride height change.
I decided to use Nick's recommendation to relocate the LBJs .250 inward, to avoid needing offset bushings to get additional adjustment.
I will let you know soon how it all worked. Tom