Can ayone tell me how to wire in an MP3 input to a stock 87 Grand National radio ? What I'd like to do is similar to what I've seen on eBay but I dont want to drill a hole in the front panel to bring out a jack. Instead, I want to bring it out the rear and under the dash for a more discrete job. I've seen the cassette tape method but prefer to do it without the "trick cassette" method. Anyone know how to do this on either the slider bass/treble radio or the EQ radio ?