You might want to get some other advice also because if you ask me I say go as big as you can. It's not always the best idea but it seems to be my philosophy.
Unless you have the tools an experience to change the motor mounts and pinion gears probably have to change your exhaust manifold and throttle Servo positioning. sounds like a lot to go through when it comes with a really strong motor. Upgrading 2 a really strong motor it's just going to cause...