Can I take the ignition coil out of my 1965 dodge challenger and replace it with a ECU?
If I can, how will I go about doing it?
Can it be a simple replacements?
There are a number of ways to go solid-state ignition and there are a few open source projects that allow you to build your own ECU and loom and utilize an ignition system from something else.
One system that instantly springs to mind is MegaSquirt which is a programmable ECU project that uses Ford EDIS parts. Depending on the engine configuration you have (I couldn't find a 1965 Dodge Challenger as everything I read suggested they started in 1970) you can use parts from the EDIS-6 or EDIS-8 for either 6-cyl or 8-cyl engines. You need to add a trigger wheel and sensor to your crank and you can then disconnect your distributor and coil.
If you want an off-the-shelf solution, there are a number of companies which offer these too, such as MBE, JENVEY, WeberAlpha, etc...
these 2 parts are not the same
an ECU in modern cars uses a vast array of sensors to direct different systems to work in harmony.
a coil is what generates your electric charge that runs through your spark plug. All cars require these either as a single coil like in your challenger, a coil pack which is found in many cars between the later 90s and late 2000's, or coil over plug which is what most modern cars use today. no car can run without some sort of ignition coil or a bad case of dieseling or magneos or a de facto diesel engine.
what you are probably looking for is a MSD (multi spark distribution) module. This creates more than one spark per combustion cycle to help burn all the fuel and get the most power you can out of the fuel charge.
You could however modernize the car and engine but purchasing aftermarket fuel injector rails, a coil over plug or coil pack setup a mass airflow sensor, throttle body with position sensor a knock sensor and some other components. This setup would then be controlled by an ECU but that ECU will need to be tuned for your engine.
Look at the MSD Performance ignition parts. They engineer a number of solutions from points/distributor adapters to full-on EFI solutions. Call up Summit Racing if you are confused; those guys are very knowledgeable and friendly about helping with the older engines and newer technology.