I have a slight problem that I was wondering if anybody has an answer for. I just swapped a 3.8L out of a 96 mustang for a 4.6 also out of a 96 mustang. i cant start the car without a problem. It starts on the first turn of the engine, but only runs for about 2 seconds. I am completely stumped. The only thing I didnt take out of the original 4.6 mustang was the wiring harness under the dash. I read somewhere that its possible to use it you just have change some wires around but i could never find anywhere thats says what wires. any help would be greatly appreciated.  

Sounds like your fuel pump isn't staying energized.  Check the fuel pump relay circuit.