Ford 6A-D7AF-19A241-AB Have a nice looking (other than some clown cut the wiring harness ... ) Aeronutronics Ford slide bar am/fm stereo. I can't find any info on it and was wondering mostly if it needs an 8 ohm speaker or if by the later 70's Ford had changed to 4 ohm ones? I want to bench test it at full volume but would like to match the right ohm speakers first. I did test a pair of 4 ohms wired in series on each of the 4 channels and it has decent sound and power. But I didn't crank it up to see what it sounded like at full volumn - just tested to see if each channel was working. Any thoughts on this old radio?