You should just put your seat in the car and measure up about 6" from the harness holes. That should put the bar in the right place. The important thing is for your harnesses to pull you into the seat and not push down on your shoulders. The installation instructions will have an angle for the harness to from your shoulders to the bar.
The caster bushing come in 2-4 different hardness levels and they are all harder than the ES bushing material. I think that the ES stuff is Poly and the caster bushing is delrin.
They will provide some additional caster over what you will get with the caster/camber plates but I don't know how much because I have never tried to measure it. I max my caster out with the plates and leave it.
#67 Sentra SE-R
2007 NASA-MA Rookie of the year
2008 NASA-MA PTE Champ
2009 NASA-MA PTE Roadkill
2010 NASA-MA PTE "If it can break, crash, or burn.... it will."