David, I am presuming there is a motor with a gear on top, and a gear on top of the shaft? Flexidrive? That goes to the prop.
i am also assuming the380 and 540 refer to the brushed motor can sizes? Unfortunately the motor shafts of the two motors are different sizes, and in any case the gears need to be th3 same pitch so they mesh properly.
Motors in this size are very common and inexpensive. However getting the right combination of gears for motor/shaft may be an issue.
Is all this right so far?
Ashley