I was told that for new head gaskets for my cat would be late model SC 3.8L? will they work on my 1988 cat?
The biggest thing is to make sure the heads are perfectly flat. If they're perfectly flat, you can use felpro's made for your 88 3.8L. Something a lot of guys do is use copper gasket spray on both sides of the gasket, and when it gets tacky, reinstall the heads.
I've owned three 3.8's, two birds and a Sable, and have replaced the HGs on all three. Actually, the current bird is on its second set. Listen to Tbird232ci and ensure the heads are perfectly flat. You don't want to do it twice.
Why not just use the ones that are called out for. I think that the SC Hgs are the same as the NA gaskets. Autozone shows different PNs for an 88 3.8 NA vs a 92 SC. Ive put the Felpro set on my SC which runs 16psi with no problems so far. I do use an ARP Head-stud kit which seems to help alot of HG issues. I have heard that some people use the SN-95 mustang gaskets but I'm not convinced they are much better.
(http://www.sccoa.com/forums/showthread.php?t=9796&highlight=mustang+head+gaskets)
You can post at SCCOA about NA engines but I think that you could use one over the other. Since the PNs are different, I would be cautious. I do use the copper gasket stuff though. I agree with Tbird232ci, flatness is key.