I have the Aerospace kit installed. While the front track change is in the neighborhood of 1/4" I would have to guess that the rear was not moved much at all... I would estimate 1/16 to 1/8" at the most. The only difference is the thickness of the 'hat' on the disc is somewhat thicker than the original steel drum. The axles are in the same place on both setups so there is no variation there.
As Jay states...the rotor hat on my Wilwood kit is a bit thicker than the drum...I would say that it widened the track a little over 1/8", maybe 1/8" per side, as I could not fully engage the lug nuts when I was finished (though my lug nuts are aftermarket and have slightly more threaded area. I installed longer studs and have had no problem...I don't think it's enough track change to cause tire clearance problems. But then again, I haven't really taken exact measurments.