Will a 04 Mazda 6 motor fit in my 07 Mazda 6

There are 2 engines made for the mazda 6. There are also changes in the engines over the 2 years that you are describing. If you are able to tear down the engine to a bare block and notice that there are no internal differences, such as cams, then it should work if you put back everything onto your 2004 engine from your 2007 engine. That would mean replacing all of intakes, manifolds, etc, and using the original wiring harness from your 2007. However, I would recommend finding the correct direct swap engine to avoid issues in the long run or messing up during the process.

does a 2005 mazda engine fit a 2006 mazda

If you have a 4 cyl engine then it's year specific for 2005... So get a 2005. Unless you can tear it down like the other guy mentioned and make changes. If you have a V6 then you can use a 2006 in a 2005. Those years interchange. It's always recommend to stay with same year if you can. Good luck.

Has anyone used a 2006 3.0 in a 2003 mazda 6 having trouble getting injection pulse after changing motors out.

What motor will be a direct swap for a 2007 mazda 6 2.3 liter?

quisiera cambiar mi motor mazda 2.3 2007 por uno V6 3.0 2007 es posible y que otros componentes electrónicos de deben cambiar?

Si