Personally I think you should stick with the geared 280 on this plane. If memory serves my correctly this Tutor would be a bit small of a plane for a speed 400. ( the 400 is almost 2x the size of the 280) Not only do you have the weight difference of the motor, but you will need larger batteries for the speed 400. Every ounce always matters with an airplane, but even more so with a plane that doesn't weigh that much to begin with.

Get the speed 280/gearbox/ESC for the Tutor, and then you will still have all the goodies for the old timer.

Just my $0.02