Its measured from the center of the tyre contact patch to center of tyre contact patch. For the struts i'd use either the XT130 strut and the hilux/pug brake upgrade or use RA40 celica struts and make everything custom.
knowing how much is to much with regards to track is kinda touch and go, it takes testing and what not. What i would do, instead of running massive negative offsets, run stupid fat wheels. that way u have the dish but the center of the contact patch is still pretty close to where it should be.