Another magnum swap thread

Stock ECM can be tuned with SCT software for almost anything you want it to do. You call someone who does tunes, tell them your combo, and they sell you a handheld tuner box loaded with the calibration you need. You can load that calibration into your ECM, and you can even purchase additional calibration files for later upgrades. This only applies to OBD2 ECMs with three connectors. The single connector OBD1 ECM is not programmable.
Harness is easy to build yourself, even if you are not experienced. Just get a complete engine harness from local self service salvage yard. You keep the connections you need and remove the unused wires left over.
Last harness and ECM I got cost about $150. You pay a lot when someone else is removing wires for you, but it is easy to do.