Need help, motor swap

06 Mazda 6
Hopefully someone can help.
So I just bought a 06 Mazda 6 and I was told when I bought it that the guy put a 2010 Mazda 3 motor in it. The 06 Mazda 6 stock has a 2.3L and the 2010 Mazda 3 has a 2.5. Now for one Im not 100% sure what motor is in it and I need to know. Theres a 2.5 stamped on the block but not 100%. When I purchased the car the clutch was slipping(taking extremely long to get into each gear and severely lacking acceleration. Because the motor swap I am unsure which clutch kit to purchase. Any help would be so very greatly appreciated.

So the clutch finally went. Car is now down and I am unsure if I need to buy a clutch for the 06 mazda6 or the 2010 Mazda 3
Portland, OR USA
2004 6s Wagon
Bummer. Pull the clutch out of yours and take it down to the parts store and compare it to both.
Or buy both online and return the one you don't use.
Good luck.