Hemi won't fire
The ECM needs to see the body controller if the ECM came from a car with security system. You need to know a Dealer that can upload an update for a vin number from a fleet vehicle. I got my vin number from a fleet vehicle for sale on E-bay it was a Ram pick-up. Down load a update into your ECM through the OBDII port using that Vin. from E-bay. It will bypass the anti theft and it will start.
My son and I pulled our hair out for 2 Months. You must personally know a dealer to do this . Most will not. The only other way is to put up the cash for a fleet ECM. and you won't know until you try it.
There is no way of knowing unless you are at the dealer and keep trying different Vin numbers as we did. We went through many at least 10-20 until we found one. It was a NY state truck for sale on E-bay. Plain Jane No A/C , P/W or power anything. 2003.
We were using a Painless wire harness.