So going off of the post from tom2112 explaining key fobs...
"5) When you put your key into the ignition, the fob’s transponder responds to your car’s ignition and replies with a special code."
"6) Any fob’s transponder can NOT be reprogrammed to work with your car. "
"7) A transponder chip from YOUR car’s fob can be transplanted into another fob, and that fob will start your car, as long as you transplant your physical key along with it."
"8) The physical key will always turn your car’s ignition and door locks, but without the correct transponder, your car will not start."

I have to put the replacement transponder into a new fob because I have to match the physical key and the replacement ignition once I wire it back up under dash like you said? Or am I totally wrong again? because it says another transponder can not work with your car.