>Personally for good mechanical strength I'd recommend using a pair
>of RCA jacks in the dash.  1/8" phone jack is pretty fragile, and
>the plug is even worse, although a right-angle head helps.

Or have your 1/8" jack on a pigtail with a grommet in the dash.  May
not look as nice but it will keep on working a lot longer.  I try not
to rigidly connect small phone (3.5/2.5 mm) to anything weighing more
than a few ounces.

Yours,
David