Outer Limits 4x4 Board

I am in the middle of a build which involves putting a ln106 hilux (1990) dual cab body onto a gq patrol chassis and just trying to work out where to sit the body so that tires clear.
On the hilux's it is common practice to move the front diff forward 30-40mm which allows bigger tires to fit without scrubbing on the back of the guards.
I am running drop boxes on the gq chassis which push the front diff forward approx 10mm so I am thinking that I should put the body on so that is is roughly 20mm backwards of the front diff (same effect as pushing diff forward) to get the 30mm.
Does that sound right? The thing I am not sure is that the hilux's are leaf and patrol is coils so I imagine they behave differently under full flex/compression. Is there a more sophisticated way to work out where the body should sit of is it just a case of getting it close then flexing it up and seeing what hits where.
Any thoughts?

BTW the patrol/hilux will be running 4inch lift and 33inch tyres (basically the max my engineer will allow) but may look at 35's as play tyres down the track.

Cheers
James

What about removing the coils, strapping the diff to the chassis at full compression, with the 35 on placing the body with gaurd in the centre of the wheel arch?

If that makes sense.....

when i put my 45 cab on my 80 series chassis i did as wicked suggests

pull out the springs and place your cab so the tyres clear at full compression!

Make sure they clear the rear of the guards at full lock too.

Cheers