C5 corvette rear differential modification?
If you want to use the rear IRS system from a specific model... you pretty much have to use all the assoicated components or its not going to work without alot of design analysis to prove that it can and will work congruently without going into bind. This is your answer to why you have "yet to find anyone doing anything with the C5 rear suspension." It was designed around the transaxle...
Your only real option is to use a C4 IRS with the C5/6 front suspension... as it will be your only option with your requirements and use of a back seat.
Good luck



