WolfpackRadicals makes adjustable motor mounts so you can put different motors in your fusion up to a .28. But the problem you are going to run into is the basic components , like the ball bearing and clutch are so weak they will not hold up to the increase in rpms, torque and power. Do yourself a favor and sell them , the high output motors will tear them up.
I'm sorry, that just doesn't make sense to me.
Are you talking about the ball bearings in the wheels? I have run my GTR and Fusion with the third gear disabled (and only first gear too, just to try it) and that never broke anything.
I would be more concerned about the belt, but I don't really care if it wears out faster, the difference in speed (speed of the belt) isn't that great.
It might be true that the ball bearings don't handle that high speeds, but how do you know that for sure? And how much abuse can they take? Maybe they don't have any problem at all with higher speeds for all we know.
And the clutch? Well, my Fusion can spin its tires (rubber, not foam) and that means the clutch can already take maximum stress of what the tires can provide. If you increase the horsepower or torque of the engine without increasing the grip, then there will not be an increase in stress on the clutch either.
So in short I just don't agree with you at all, and I would like to try with a better engine, because I've heard of others doing it with success too.
Just as a side note, I've put an electric 2 kW system in a very cheap and small 1:12 Lancer SP3 car, and I've put 8-turn engines running 3-cell LiPo that were so powerful and go so hot that the wires melted right off the motor I was told by others that "Forget it, you're going to melt the gearbox", none of that happened, and nothing else broke. I've run that car quite a bit since. Not that this has anything to do with the Fusion and GTR but I want to point out that there are some cars that can take a lot of modification and abuse without burning up.
And besides, why would Schumacher create higher greating kits for their cars if they can't handle the power required?