For a 2004 Mazda 3 with a 2.3L engine will a 2006 or 2007 Mazda 3 2.3L engine fit?

Yes, a 2006 or 2007 Mazda 3 2.3L engine should fit into a 2004 Mazda 3 with a 2.3L engine, as they share similar engine designs and components. However, it's important to verify compatibility with specific parts like the engine control unit (ECU) and any necessary wiring harnesses. Additionally, checking for any differences in emissions regulations or mounting points is advisable before proceeding with the swap.