You would want a higher caster - the straight measurement on mine when I had an alignment was around 8.3 deg. To give you a better picture, the wheel was closer to the front edge of the wheel well arch than previously, where the caster was 6.x degrees.
This is how mine is right now after alignment.
It might not be too obvious here, but if you compare mine (yellow/beige w123) to the others the positioning of my wheel is not as it was above (this was prior to the alignment). Other w123s beside me had better caster, their front wheels were more forward in the wheel well than mine.
