If I use a photo resistor, to detect the beam break on the finish end, what is the best way to attach to the gpio. The distant would be at least 120 feet.

I would have a start laser and resistor and a finish laser and resistor.

I am looking to build a timer for the 40yrd dash for my high school. What would be the best sensors to use for that and what do you think would be the best way to connect the two sensors.