Wow, building an IRS yourself. Quite an undertaking, your going to learn a whole bunch.
There are a few cars that have been built with C4 corvette rears. As long as you plan to use the stock hub to hub width it is a pretty easy swap, just go with coil-over shocks instead of the transverse spring. Stay away from narrowing the rear width too much, as other issues start to crop up and need to be resolved.
Look for the Beach Cruiser first gen Camaro and the P1800 on this site. Full custom installs, using much of the factory parts with custom install mods to fit the build.
https://lateral-g.net/forums/show...ighlight=p1800
https://lateral-g.net/forums/show...ghlight=camaro
Regarding the C5/C6 rear end and transaxle, that setup tends to blow out the back seat of most cars. There is one build on this site (1960's vintage XK120 Jaguar) where they mounted the C5/C6 Vette IRS suspension and brakes on narrow frame rails, and are using a 5th gen Camaro gear case, with modified torque tubes.
https://lateral-g.net/forums/show...ghlight=jaguar
Hot Rod Magazine did a comparison of systems in existence a few years ago. It gives some good points of consideration when thinking about an IRS swap, especially limitations of the different set ups.
http://www.hotrod.com/how-to/chassis...or-musclecars/
If you are looking for an outright swap with a complete rear, there is a first gen Camaro that is using a Nissan 350Z rear end (build thread is on protouring.com), lots of other cars and trucks using 1990's Ford Thunderbird IRS, and I've even seen a 69 Camaro that has an IRS from 7-series BMW, with cantilever shock set up.
http://pacificfabrication.com/barrys-camaro
Got your work cut out for you. Just picking the type of IRS is a chore by itself.