2003 ford focus

You can as long as it the same size engine....

What do i look for to find out the actual engine size for my car with out changing any other component like harness and hoses?

You can put any engine in any car you might have to have the computer and complete harness to the one yoj get the moter out of hell we put a 95 linckln ls or watever the badd ass duel ovefhead cam v8 in a i think a 3) roadster but we had the whole harness and computer for the moter it all came out of 1car so wat exactly are you trying to do is the question by the way the lincoln ls v8ran perfect really fast and squirmy in the roadster the check engine light works koeo and it does not illuminate with the engine running the aifbag and track controll lights are on but those will soon be intergrated kn the system as well as a couple of things have to be re engineered for safety reasons