compilation of what i learned with head unit installation

[rwhite]

Had to search far and wide for info on installing a aftermarket head unit with the bose system so here is what I found that actually works:
Dash adapter: you can use the scoshe or Metra for the same year maximal. Apparently the Metra allows for a caged install and the trim face can still be used. It is supposed to be cleaner. I used the scosche. It turned out pretty well but there are some gaps and the trim face cannot be used.

Harness adapter:
I used the scoshce nn03. Made things easy.

Line level converter:
You have to have this because the bose speakers are individually amped. If you don't reduce the gain you risk blowing the speakers. I used the scoshce fai4. The slc4 and the oem4 will all accomplish the same thing. If your converter has input and output gain adjustment turn the inputs all the way to zero or - and set the converter to factory amp. You can set the gain of the output a few ways. One is to turn the stereo to 3/4 volume and then adjust gain until you get distortion. The easier way is with an ohm meter and you can do this with out power to the system. Measure resistance between the pos and neg speaker wire for each speaker ( grey to grey/black or purple to purple/black) adjust the gain to 2 ohms.

Antenna:
You need a diversity adapter. I used scoshce uaa1. Our cars have 2 antennas, the mast and the window. The adapter cuts out one of them. You have to experiment and see which antenna gives the best reception. Install one way and if you don't get good reception flip the connector around. Beware the connection and the stock antenna wire are flimsy. Don't kink the wire or bend it during install or you'll lose reception. One you have it hooked up tape the connector together. I read all kinds of things about power amplified antennas and having to hook up the power wire. Believe me none of it works. Just find which antenna wire works best and don't kink the wires.

That's it. The stock speakers if in good shape put out some good sound and bass. The head units are crap though.

[rwhite]

Couple of clarifications:
When setting the gain measure the ohms on the output side only of the LOC and across the pos and neg wire for each speaker.

PAY THE $9 FOR THE HARNESS ADAPTER! Don't try and hack into the stock wiring harness. The adapter is cheap and does 2 things for you. It makes a clean install and it allows everything to be wired up and set on the bench so it's then plug and play instead of monkeying around trying to splice wires in the car.

Grounds; run all the grounds to the chassis behind the radio. To my knowledge the original system is grounded through the antenna. When you use the diversity adapter you lose the ground so you have to run a ground to the chassis.

FWIW the alpine I installed has rca jacks as well as a function to defeat or turn of the internal amp. I didn't have the rca adapter to try it but it's my understanding that defeating the amp has the same effect on the regular speaker outputs as using the rca jack (as far as power output). Anyhow defeating the amp did not produce the same sound quality as using the LOC.