What i did exactly was take the radio out of the dash and cut the red, white and black wires leading from the cassette player. The wires are as follows: red = audio right positive, white = audio left poisitve, black = ground for both the left and right. I then stripped and soldered these wires to a headphone extension cable from radio shack and installed the jack inside my center console. The only downside is that you have to have a tape in the cassette player if you want to use the new auxillary connection. Most of the hissing goes away since the signal is no longer going across a tape pickup. I think maybe a ground loop isolator or somethin of the sort could fix the rest of the hiss. But thats a project for later.
