Do you need an avr counter that can measure for 40Mhz and low cost for this project? Well take a look at microcontroller project : avr counter created by Murray GreenMan. This microcontroller project also give you some interesting feature like : 8 digit LCD display and there is an optioanal PC telemetry so you can watch the output on a PC."The counter contains only three inexpensive ICs (well, add a regulator and three transistors), and operates from 6 - 15V DC at about 25mA. The most expensive single item is the LCD display, which is an industry standard 16 x 2 dot matrix module, which can often be found used or at bargain prices. This isn't a kitset, but the parts are easily obtained, and the circuit can be built using any prototyping technique, or you could design your own PCB. The prototype was built on a small commercial strip board." [Link]
