In the back they should fit. I'm speaking from doing the reverse. Using Z06 wheels to replace the sawblades. The back Z06 wheels appear to be more or less in the same spot relative to the wheelwells than the sawblades. Like BRICHC4 said just give it a try.
Well, my 90 C4's rims with new Firestones where just sitting and collecting a lot of dust. The ZO6 tires were toast. The C4's worked great and have been on the car for two months now. Fit fine and I get "where did you get those great wheels?"
It's late here and getting cold so I have time on my hands to look at the forum again.
I might be selling my 1990 chrome rims in a short while if you're interested. I love them to death, but am dying to pick up some 11" wide rims to handle 315's.