[1speedbike]

I don't know where to help you find another transmission, but it should be explained that you cannot just ask for horsepower and "hold the torque" like you're asking. Horsepower and torque are intrinsically related. Torque is a measure of the force going to the wheels. Horsepower is a measure of how many times that force is transferred to the wheels per unit of time (power). I guess a way of explaining it is that your particular engine will make a certain amount of force to get the car moving, and the horsepower is a measure of how effectively and how often that power gets to the wheels. Horsepower will always equal torque at 5252 RPM because at that RPM the mathematical relationship between the two balances out to 1.

Basically, the only solution would be to limit your power/torque overall to protect the gearbox, or to upgrade the gearbox itself. You can't limit the torque but have the same number of horses.