ok i have a 1986 suburban c20 454 and i can not seem to wire the radio right and i cannot find good diagrams to help also i habe a extra connection that is two wire one is orange and one yell i cannot find the cennecting point please help

 

yellow should be 12v constant power. there is another power wire there but it is accessory power. Might be red, but doubt it, its probably 2 tone.

and the 2nd orange wire should be the illumination wire for the light in the original radio. Most aftermarket radios will not use that. So just tape it up and leave it alone.