There seems to be a lot of confusion about the replacement of a Mach 460 head unit in a 2001 Mustang. I switched mine out with the help of many people in this forum, so I figured I’d compile all of my information together and post it. This may apply to the 02 and 03 setups, but I am not sure if the system is exactly the same. Someone would have to verify that. First, an overview of the system. The system consists of 4 tweeters, 4 subs, and 3 amps. I’m not positive on the size because I’ve never removed them. I believe the subs are 5x7s though. The first amp is actually contained within the head unit and runs all four tweeters. The second amp runs the front subs and the third runs the rear subs. The reason that things get interesting replacing the head unit is that you need to send an amplified signal and an un-amplified signal to the amps that run the subs. Here’s what you need to replace the head unit: 1. A new head-unit with RCA outs on it. It is ideal to have a high-pass and low-pass crossover both built in as well. If you don’t have those crossovers, you will have to use the crossovers listed below in 4 and 5. 2. Scosche Sound Kase SKFD223 - $25 This fills up the hole that is left underneath your new head unit. The space is filled with an area that holds 3 CDs. http://www.cardomain.com/shop/item.pl?sku=SCOSKFD223 3. METRA 70-5519 Harness - $18 This is the only harness on the market that will work. http://www.partsexpress.com/pe/pshowdetl.cfm?&DID=7&Partnumber=265-790 4. Low-pass crossover for your subs (not needed if your head unit has a low-pass crossover built in) Go to http://www.partsexpress.com and search for “FMOD” and choose the frequency that you like 5. Bass Blockers for your tweeters (not needed if your head unit has a high-pass crossover built in) http://www.crutchfield.com/S-P3Rgdy...asp?s=0&cc=01&g=761&est=&search=bass+blockers Choose the frequency that fits your liking. The key to the entire setup is the Metra harness. This is the ONLY harness on the market that is completely plug-and-play with the 2001 Mach 460 system. I purchased the Best harness (which was originally recommended to me), and found out the hard way that it does not work. When wiring the Metra harness to your radio, follow the following guidelines: - Combine all grounds from the Metra harnesses to the ground on your radio’s wiring harness. - Combine the amp turn-ons with the ignition-on power on your radio’s wiring harness. - Plug the RCAs from the back of your radio into the Metra harness. If you don’t have a low-pass crossover on your radio, you will need to plug the FMOD crossovers in here. - Wire the L/F+-, R/F+-, L/R+-, and R/R+- from your radio’s wiring harness to the corresponding wires on the Metra harness. This will send an amplified signal to your tweeters. If you don’t have a high-pass crossover, you will need to put the bass blockers in here. Once you wire all of this, you are ready to replace your head unit. If you don’t know how to get into the center console, follow the beginning of this article: http://www.stangnet.com/tech/speedsound/ssv.html Once you get your Mach 460 head unit out, you can mount your Scosche kit where the radio used to be. Then you can just plug your harnesses into the Mustang harnesses and you’re ready to test your new head unit. If your crossovers are contained in your head unit, then you will need to set them immediately before turning up the speakers to keep from sending the wrong frequencies to them and damaging them. If you used the FMODs and bass blockers, then you should be good to go. I've attached a picture of my new head unit so you can see how it looks with the Scosche kit around it. The kit also adds 3 CD storage slots to your system, so that is nice. Overall, I have been happy with just replacing the head unit. The sound quality is pretty much the same as the original Mach 460. I really just wanted to add MP3 functionality and Sirius to my setup and this worked perfectly. If anyone has any questions about this, let me know and I’ll be more than happy to give any input I have. I hope this helps you guys out.