Hi 
There maybe reasons why what I suggest below can't be done but:- 
 
Would it not be more simple to change over the feed wires to the clock and the radio? 
Just connect the positive wire to the negative terminal and vice-versa. 
 
If the radio has an asymetrical conector plug which can't be rewired then cut each wire and reconnect the ends to the other wire. 
		
		
		
		
		
		
		
	
	 |