have a 2004 Mazda 6 Sport wagon with the 3.0 L V6 & 5 speed auto. 135K miles & still runs good with a full air intake & 225-45-17 Hankooks but otherwise stock, but eventually when engine goes, would it be possible to replace it with the 2009 or newer Mazda 3.7L V6. Possible emission or other computer problems?