Does the back of your stereo look like this.
Here's some pics of mine on my 88 gt
Mach 460 is 4 woofer 4 tweeters and 3 amps.
Factory wiring is use for tweeter and the woofer is stand alone and controled via the front ampli.
If you can get the rear module (2 woofers, 2 tweeters and 2 amps) be sure to get the wiring intact. No wire cut. Otherwise this will be a pain to hook.
Do you have pics of what you already have on your car