There is at least one Suburban out there with an IRS from a Corvette. I think I saw pictures of it on the HAMB.
I doubt you'll be able to decern a difference in ride running an IRS. A leaf spring rear suspension in good condition will ride pretty nice.
At a swap meet Saturday I saw front and rear suspension from a 2000 Corvette with the rear mounted transmission. Going that route under a Suburban might be unique, and moving more of the weight to the rear might improve both handling and ride.
