This forum has been such a wonderful source of information, however I can't for the life of me figure this bit out.

I have an aussie 1991 AllTrac TCR21 Previa/Tarago that I want to get a couple inches of lift and bigger wheels on. I and am intending on doing a coilover conversion in the front and coil swap for the rear. Unfortunately I've run into some trouble with the rear coils, with the Aus local version of the 8088 coil springs having an ID of 100mm and the coil I've pulled out of my Prev is more like 115mm. Can anyone point me to more info on this? It was tough enough to find a 'Mustang' spring in aus, and everything I can find suggests 100mm ID is right for the 8088 so I'm pretty confused has this got to do with the IRS?

Also, can someone confirm the rear coil ratio? 2:1 was my guess based on Tim's 1in coil free height giving 2in lift, but some combination of stiffness etc would impact this so confirmation would be amazing.

Thanks in advance!