yes, you can have the rods removed! It is called a "hardware removal" surgery and I had it done 15 years ago. It is a great feeling to get the metal out of your back. BTW, it does not matter if the bone has grown over the metal, they can still cut the bone away and take out all the hardware.
Maybe you misunderstood the doctor OR he may have accidentally mistold you that he put 2 Harrington rods in, but I know about HRods...they don't undo and migrate. If xrays show only one, there is only one in there. I am doubtful that any orthopedic doc will remove the rod(s) just because you want them remove, as it IS your back/spine. BUT...if you are having pain, and since it's been since 1978, they might do something.