For the tachometer, I'd measure the amount of time (microseconds) it takes to observe 9 cycles of the input clock. Then, divide that number by 10 to set the period of the output signal.
Likewise, for the speedometer, I'd time 9 cycles of the input clock. Then divide by 14 to set the period of the output signal.
The above would take place continuously so that that the output signals track the input signals in the proper ratios.