The two cut wires are radio power and radio lights, ground is supplied thru the chassis thru the bracket and connection to the dash. The blue-red wire is the light power thru the dash light dimmer circuit from a three socket block with a blue-red lead. The power comes from a black wire jumper assembly marked C6ZB-18A919-A from the same three socket block as the backup lights to a black wire pin on the radio. The two cut wire leads are the same as a regular AM radio and can be unsodered from an AM and reused. The three pin connector is for the speakers. Being it is intact is good. The odd pin is the right speaker, the middle is common (aka return) and the remaining one is the left speaker. The under dash speaker lead may be available or not, p/n C6ZB-19A041-A. It feed the door harnesses which is available.
Jim