If that is actually something that Camero guys do
you might want to look up a Camero group.....
Puzzled as to why??

Visual?? Won't be able to see it, so it's not
a visual thing.

Performance?? To me it would be hard to get all the pivot points exactly the
same in the F body (Camero is an F body right hehehe)
And there are Camero suspension mods available that would be just as good
as an IRS, except if you are at the extreme of road racing classes.

Seems like a hell of a lot of trouble for no real world gain...
But maybe the Camero guys know something I dont. :-)

Hey Jeremy!  Here's a link with a C4 IRS conversion of a '69 Firebird. Just
a few pics which may be of help. I ran a few searches and one guy in a
NewsGroup said that it's a fairly easy swap, almost a direct bolt-in, except
for the rear springs. Another guy said that you have to completely remove
the gas tank and stick in a fuel cell. I hope this helps. Here's the link:

http://www.pro-touring.com/waynedue/chris_baldwin_69_firebird_project.htm

Here's another link where you can get in touch with the guy:

http://www.pro-touring.com/waynedue/