I am almost done with the V8 engine Swap on my 2007 mustang V6 it was more work than I thought but right now I have the engine and transmission installed, I also used the whole harness from the donor car, I changed the steering wheel column, the instrument cluster and the ECM. I have the key from the donor car but my problem is that it wont run. The security light on the instument cluster is flashing quick and when I try to start it nothing happens. I want to know if I have to reprogramm the key or what else can be wrong? I will really appreciate your help with this issue I want to drive my car!