FYI, A 93/28 64P for an F104 results in a potential top speed of 29.13 mph if the motor can still push hard enough. That is very aggressive gearing, but I've run similar on my F103, avatar pic. It gets a little hot and there are no brakes to speak of. I do feel the top end was soft, trying to rev more, but out of torque. Gearing the F103 back to a 24 pinion, it kept the same top end and accelerated better, cooled down and I also magically had brakes again.