got a radio with aux-in!
I could not find a convenient spot to put a 1/8 stereo jack on the body of the radio then i decided to go with a "pigtail". It was cheaper to buy an "extension cable" with a male and a female 1/8 stereo jack and cut it than to buy the materials.
Here is the pigtail from the back:
And here is inside the radio, cable is routed to the front where if goes under the circuit board:
Here is where the cable is connected. In addition two modifications have to be done to the circuit board, cut a trace between the TEL-R and TEL-L to isolate the channels (the telephone is monophonic) and cut a trace that carried the original signal to the preamplifier.
Then i now have a radio with an AUX input! :-)
Since the car is a hostile environment with a lot of vibration that can wear the insulation of cables it is better to provide additional protection for all the cables. I use an expandable braid that is easy to work with, provides good protection and gives a neat appearance.