I tried and bought a wiring harness for my 88 vert hooked up everything correctly and the stereo didn't even turn on. the guy that had the car before me cut the wiring harness off for the speakers so I allready had to sort those out (done) the rest I'm goina have to do the old fashioned way so...
where is the best place to hook up the canstant and acc leads and ground?
it's a pioneer deh6600 that I have and it works because I got it in my truck right now.

 

look under the radio, is there a large silver octagonal shapped box with a bunch of holes in it? That is your factory amp if you do and there is an easy way to bypass it if the old owner has not already.

You can tap a constant at the cig lighter, or both at the fuse box. Your best tapping a fresh ground yourself......