I'll buy myself a universal today and give it a try. Thanks for the advice.
BTW I reinstalled my original Delco AM/FM stereo today and was expecting it to sound crappy, especially as the 75s only have the front speakers and mine are original. Actually, all things considered, the radio doesn't sound too bad. It's not going to damage anyone's ears but the sound it strong and the reception is better than the high-end system I replaced.
Thanks everyone;ay