i ran into the same thing on one of my volvos. i got a metra 71-1770 and wired it into the car and a metra 70-1770 to wire to the stereo. these are standard ford parts available lots of places.

http://www.metraonline.com/product.aspx?sku=70-1770

the yellow wire connects to any +12 that is always on (ie: clock ). ground wire to metal frame of dash or firewall. the thing to pay attn to is the depth of the radio, i installed a 400w unit with a large heat sink at the rear end of the unit that is real close the heater core.
pull the speaker grill in the dash and check for clearance and also windshield wiper linkage that can saw thru the wires