When i was a member of Liverpool District Motor Club, our Electronic timing system consisted of two beam of light, one for the start the other for the finish & a good quality digital stop watch. The start signal was set up to trigger the stop watch when it was broken, then the finish beam stopped the stop watch. this was for a single car at a time, but it was used to time state hillclimb championship rounds. I know the distance between the start & finish lines is extreme, but a radio signal could be used to send one of the impulses, or if you always use the same start & finish areas, you could get the local Telstra guys to hard wire it in. You could use 2 stop watches on the condition that the first breaking of the team stopped the first watch, & the second breaking of the beam stopped the second one. Or you get the car that lined up on the left hand side of the road to finish to the left hand side of the track & the right handed car to the right hand side. Put it in a fancy box with a switch to turn some trafic lights from red to green & back (single pole, double throw, centre off switch) & an orange light that goes off/on when the car breaks the staging beam & then is pushed back slightly. so cars come up to the start line, break staging beam, are pushed out of light beam, Somebody flicks switch from red to green, when cars break start beams the stop watches start, flick switch back to red so next pair know not to start, when cars cross the finish line the stop watches finish. Somebody records the times on a sheet or into a computer, then reset stop watches for the next run. 2 stop watches, some wiring & some sort of logic circuit that stops first one watch, then the other & some light beams, reflectors & bulbs, plus a couple of car batteries to power the lights. Maybe there are some electronics experts who can help you. Remember it has do deal with rain, wind & sleet, plus scorching hot days. You could even use it for khanacrosses to make it a better investment.