Ok so i have a 1999 mustang gt with 180 thousand miles on it. There is a Slavage yard about 100 mile away that does nothing but mustangs. They have over 2000 mutangs in. If I wanted to put a 2004 in my 1999 what would I have to change out in order for everything twork or ahould i just stick with a 1999 gt engine? I only ask because its making a mocking sound when I accelerate and it sounds like a piston hitting something or something of that nature.