Hypothetical 360 magnum build

If you are putting it a Durango and using the factory fuel injection just put it together. Send the PCM out and get it flashed to the specs you want it to run. You can put all the stuff inside you want but if the ECU isn't tuned to the parts it will run like ****. This isn't magic. You keep asking questions but then change your mind. If it's EFI you WILL have to change the programing to fit what you change in the engine. Keep in mind the PCM controls the transmission shifts as well. Now you have to deal with that. Unless you put a programmer on it or program in the PCM you are making a monster. I can guarantee your first program will be close but it will not be the best. Plus it's about $350 to $400 just to have it done. It can be done but it will not be cheep. A programmer might be hard to find for it at this point. It's old school now. Now on top of that if it has a Security or SKIM in the PCM you CAN NOT GET RID OF IT!!! The BCM will have to see the correct PIN from the PCM of it will not run. So you will not be able to just use any PCM out of a different vehicle. The VIN and PIN must match.