Wiring Questions

I have a couple of wiring questions on my 74 dart. Ive been working on fixing some of the dash wiring. I have the factory am radio, does anyone know what the radiuo uses for a ground? I have a red and orange wire connector, and i found the connector under the dash for this, one must be power and the other for illumination to the radio. The other wires coming from the radio are one black and one green , i assume these run up to the speaker. The orange and red connector was looped together by the previous owner, when i disconnect this and hook it back up to the radio i loose my dash illum lights. When i hook the loop back up my dash lights stay on anytime the key is on. Anyone have any ideas on this. I also found a black with white stripe (ground wire)? attached to the dash under the ashtray but i cant find where it should hook up to. The radio maybe? Thanks in advance J.R.