I have a friend who bought a 5.3 long block from a 'rebuilder' and swapped it into his 01 silverado. He says it is only firing on the corner cylinders (1 8 7 and 2). He swapped everything over from his old engine and is running stock tune, harness, etc. My only thoughts are what if he got a 58 tooth block? Would it even run? Would it fire only half the cylinders? The only way to check is looking at the reluctor wheel right?