My cobra has a 351 in it now. I blew the head gasket a couple weekends ago running a 125 shot of nitrous. I was wanting to put a 408 in it and I think now is a good time! The only thing I'm unsure of is how the computer and 408 are going to work together. Do I need a new ecu or just retune the current one? It's the stock ecu as far as I know.