jbc, I've got a 6.4 with a Hot Rod harness in my 70 Dart, so sooner or later I'm going to have to deal with this, so please tell me more or post a picture, etc.
retroron
Your harness and plug-ins are different than my older 5.9 Magnum's wiring. You will need to consult with folks with posts like the one just above this to get harness specific answers. In general though, they are similar.
Just keep in mind that each sensor and component only sends a range of specific voltages to the ECU. Having a pin-out diagram of your motor, ECU and harness handy will be critical. The Hemi wiring diagrams are more involved and complex.
Another issue that I avoided having to deal with by using a native 5 speed ECU, is that I am not running a computer controlled automatic. I installed a non-computer controlled 4 speed automatic with lock-up torque converter. the same transmission and torque converter will bolt up to your 6.4 Hemi.