Both sides should be equal. You can adjust it some with the Heim joints, unscrew all 3 equally to move the wheel outwards. You can only get 1/2 ,maybe 3/4" this way, though. The plunge joints will easliy allow this, they telescope through a lot of range of motion. You might need to move the opposite side "in" to get them equal.
Shouldn't be that far off, though, I wouldn't think. Maybe you have a bent spindle--I've heard that it's not unusual for them to be bent, not sure how you could measure to check, though.
HTH
Forrest