Been there done it. It works fine. I have a 94 Taurus SHO AM/FM/Cassette, with CD slave mounted in my 90 XR-7 S/C. The XR-7 was originally equipped with the JBL system, AM/FM/Cassette. It did not have the the slave CD from the factroy. I added the connection cable from unit to unit, and also spliced the slave power harness into the radio power harness.
That worked fine...(my original setup was modded by adding a 1991 slave CD) That worked fine until the CD crapped out.
Now I've refitted to the 94 Taurus gear, which is identical to the 96 Mustang GT Mach 460 units. They light up more bluish than the older units but I can live with that. There are a couple wires you need to "move" on the radio harness. Check out
www.tccoa.com for articles on how to do it.
Good luck and enjoy. BTW.....if you don't use the slave CD unit there is a shorting plug you will need to install in the back of the radio in order to get sound out of it. If you use the slave CD, you will not get sound until both ends of the interface cable are connected to the radio and CD unit.
Also...connections for the 92 style slave are identical to the 96 style. The newer radio should run the older slave CD no problem, but you do need to change two wires in the radio harness in order to turn the amps on! See the TCCOA article and enjoy.