is it an adaptor your talking about? That plugs into the vehicle radio harness, then you connect the adapter wires to the new head unit wires. If you were smart like me and cut the vehicle radio harness plug off you can still use a wiring diagram and connect it with the head unit harness.
'05 2wd Ranger xl with the 3.0
MODS-Alpine head unit, throttle cable mod, Black Rock wheels, FX4 lvl II axle swap, pooleo's camo painted bezel and mustang dome, painted/aftermarket headlights/tails fold-a-cover and over 100 hp in stickers