I am currently putting a vortec 350 out of a 99 suburban in my 86 blazer (carb). I sent the harness to have it rewired to a 5 wire hook up. what ecm do i need to buy for the truck? I heard a pre-97 because it didnt have the passlock, and I also hear that I need one for a 99 because the engine is a 99. Anyone know?