Jackaroo "wide track"

Greetings fellow 4 wheelers. I'm new to this site but would appreciate if anyone can help with knowledge of late model Holden Jackaroo wheel track info. I have a base model 2002 turbo diesel LWB Jackaroo with 16x7JJ steel wheels. I'm thinking of going to mags (after market) with bigger tyres. I see that Jackaroo "SE" and higher spec models come with what Holden calls "wide track'. I've checked the specification list and see that this option gives a 60mm increase in wheel track (front and rear) over the base model. Wheel arch flares are also added as part of the pack. Does anyone know what Holden / Isuzu does to the base model to get the wider track? It could be accomplished just by changing the wheel rim offset ratio (SE models have factory mags) but another way would be to change the actual axle/suspension set up. This would be expensive so I doubt that it was done this way. Any info would be appreciated. Holden weren't very helpful when I 'phoned today.