The conversion isn't as simple as you might think.
Do you intend to lower the rear? If so, you will have to deal with the fact that the IRS trailing arms will hit the shock towers. You will have to notch either the shock tower, the TA, or both. Then you will have to fab something for the snubber to bump into.
I also suggest you look into the orientation of the upper shock mount compared to an original IRS shock mount. Will an IRS shock work?